Computer science
Product of powers with different bases. Multiplication and division of numbers with powers. Degree with irrational exponent

Product of powers with different bases. Multiplication and division of numbers with powers. Degree with irrational exponent

We remind you that in this lesson we will understand properties of degrees with natural indicators and zero.

Powers with rational exponents and their properties will be discussed in lessons for 8th grade.

A power with a natural exponent has several important properties that allow us to simplify calculations in examples with powers.
Property No. 1

Product of powers

Remember!

When multiplying powers with the same bases, the base remains unchanged, and the exponents of the powers are added.

a m · a n = a m + n, where “a” is any number, and “m”, “n” are any natural numbers. This property of degrees also applies to product of three

and more degrees.
Simplify the expression.
b b 2 b 3 b 4 b 5 = b 1 + 2 + 3 + 4 + 5 = b 15
Present it as a degree.
b b 2 b 3 b 4 b 5 = b 1 + 2 + 3 + 4 + 5 = b 15
6 15 36 = 6 15 6 2 = 6 15 6 2 = 6 17

(0.8) 3 · (0.8) 12 = (0.8) 3 + 12 = (0.8) 15

Important! Please note that in the indicated property we were only talking about multiplying powers with on the same grounds

. It does not apply to their addition.
You cannot replace the sum (3 3 + 3 2) with 3 5. This is understandable if

calculate (3 3 + 3 2) = (27 + 9) = 36, and 3 5 = 243
Property No. 2

Product of powers

Partial degrees

When dividing powers with the same bases, the base remains unchanged, and the exponent of the divisor is subtracted from the exponent of the dividend.

= 11 3 − 2 4 2 − 1 = 11 4 = 44
Example. Solve the equation. We use the property of quotient powers.

3 8: t = 3 4

T = 3 8 − 4

Answer: t = 3 4 = 81

Using properties No. 1 and No. 2, you can easily simplify expressions and perform calculations.
Example. Simplify the expression.
4 5m + 6 4 m + 2: 4 4m + 3 = 4 5m + 6 + m + 2: 4 4m + 3 = 4 6m + 8 − 4m − 3 = 4 2m + 5
= = = 2 9 + 2
2 5
= 2 11
2 5
= 2 11 − 5 = 2 6 = 64
(0.8) 3 · (0.8) 12 = (0.8) 3 + 12 = (0.8) 15
Example. Find the value of an expression using the properties of exponents.

Please note that in Property 2 we were only talking about dividing powers with the same bases. (4 3 −4 2) = (64 − 16) = 48 You cannot replace the difference (4 3 −4 2) with 4 1. This is understandable if you count

, and 4 1 = 4

Be careful!
Property No. 3

Product of powers
Raising a degree to a power When raising a degree to a power degree base
(a n) m = a n · m, where “a” is any number, and “m”, “n” are any natural numbers.

Properties 4
Product power

Product of powers
When raising a product to a power, each of the factors is raised to a power. The results obtained are then multiplied.
(a b) n = a n b n, where “a”, “b” are any rational numbers; "n" is any natural number.
- Example 1.
  (6 a 2 b 3 c) 2 = 6 2 a 2 2 b 3 2 c 1 2 = 36 a 4 b 6 c 2
- Example 2.
  (−x 2 y) 6 = ((−1) 6 x 2 6 y 1 6) = x 12 y 6
(0.8) 3 · (0.8) 12 = (0.8) 3 + 12 = (0.8) 15
Please note that property No. 4, like other properties of degrees, is also applied in reverse order.
(a n b n)= (a b) n
That is, to multiply powers with the same exponents, you can multiply the bases, but leave the exponent unchanged.
- Example. Calculate.
  2 4 5 4 = (2 5) 4 = 10 4 = 10,000
- Example. Calculate.
  0.5 16 2 16 = (0.5 2) 16 = 1
In more complex examples There may be cases when multiplication and division must be performed on powers with different bases and different exponents.

In this case, we advise you to do the following. For example,

4 5 3 2 = 4 3 4 2 3 2 = 4 3 (4 3) 2 = 64 12 2 = 64 144 = 9216
An example of raising a decimal to a power.
4 21 (−0.25) 20 = 4 4 20 (−0.25) 20 = 4 (4 (−0.25)) 20 = 4 (−1) 20 = 4 1 = 4
Properties 5

Product of powers
Power of a quotient (fraction)
To raise a quotient to a power, you can raise the dividend and the divisor separately to this power, and divide the first result by the second.
- (a: b) n = a n: b n, where “a”, “b” are any rational numbers, b ≠ 0, n is any natural number.
  (5: 3) 12 = 5 12: 3 12
Example. Present the expression as a quotient of powers.

Each arithmetic operation sometimes becomes too cumbersome to write and they try to simplify it. This was once the case with the addition operation. People needed to carry out repeated addition of the same type, for example, to calculate the cost of one hundred Persian carpets, the cost of which is 3 gold coins for each. 3+3+3+…+3 = 300. Due to its cumbersome nature, it was decided to shorten the notation to 3 * 100 = 300. In fact, the notation “three times one hundred” means that you need to take one hundred threes and add them together. Multiplication caught on and gained general popularity. But the world does not stand still, and in the Middle Ages the need arose to carry out repeated multiplication of the same type. I remember an old Indian riddle about a sage who asked for wheat grains in the following quantities as a reward for work done: for the first square of the chessboard he asked for one grain, for the second - two, for the third - four, for the fifth - eight, and so on. This is how the first multiplication of powers appeared, because the number of grains was equal to two to the power of the cell number. For example, on the last cell there would be 2*2*2*...*2 = 2^63 grains, which is equal to a number 18 characters long, which, in fact, is the meaning of the riddle.

The operation of exponentiation caught on quite quickly, and the need to carry out addition, subtraction, division and multiplication of powers also quickly arose. The latter is worth considering in more detail. The formulas for adding powers are simple and easy to remember. In addition, it is very easy to understand where they come from if the power operation is replaced by multiplication. But first you need to understand some basic terminology. The expression a^b (read “a to the power of b”) means that the number a should be multiplied by itself b times, with “a” being called the base of the power, and “b” - power exponent. If the bases of the degrees are the same, then the formulas are derived quite simply. Specific example: find the value of the expression 2^3 * 2^4. To know what should happen, you should find out the answer on the computer before starting the solution. Entering this expression into any online calculator, search engine, typing “multiplying powers with different bases and the same” or a mathematical package, the output will be 128. Now let’s write out this expression: 2^3 = 2*2*2, and 2^4 = 2 *2*2*2. It turns out that 2^3 * 2^4 = 2*2*2*2*2*2*2 = 2^7 = 2^(3+4) . It turns out that the product of powers with the same base is equal to the base raised to a power equal to the sum of the two previous powers.

You might think that this is an accident, but no: any other example can only confirm this rule. Thus, in general view the formula looks like this: a^n * a^m = a^(n+m) . There is also a rule that any number to the zero power is equal to one. Here we should remember the rule of negative powers: a^(-n) = 1 / a^n. That is, if 2^3 = 8, then 2^(-3) = 1/8. Using this rule, you can prove the validity of the equality a^0 = 1: a^0 = a^(n-n) = a^n * a^(-n) = a^(n) * 1/a^(n) , a^ (n) can be reduced and one remains. From here the rule is derived that the quotient of powers with the same bases is equal to this base to a degree equal to the quotient of the dividend and divisor: a^n: a^m = a^(n-m) . Example: simplify the expression 2^3 * 2^5 * 2^(-7) *2^0: 2^(-2) . Multiplication is a commutative operation, therefore, you must first add the multiplication exponents: 2^3 * 2^5 * 2^(-7) *2^0 = 2^(3+5-7+0) = 2^1 =2. Next you need to deal with division by negative degree. It is necessary to subtract the exponent of the divisor from the exponent of the dividend: 2^1: 2^(-2) = 2^(1-(-2)) = 2^(1+2) = 2^3 = 8. It turns out that the operation of dividing by a negative the degree is identical to the operation of multiplication by a similar positive exponent. So the final answer is 8.

There are examples where non-canonical multiplication of powers takes place. Multiplying powers with different bases is often much more difficult, and sometimes even impossible. Some examples of different possible techniques should be given. Example: simplify the expression 3^7 * 9^(-2) * 81^3 * 243^(-2) * 729. Obviously, there is a multiplication of powers with different bases. But it should be noted that all bases are different powers of three. 9 = 3^2.1 = 3^4.3 = 3^5.9 = 3^6. Using the rule (a^n) ^m = a^(n*m) , you should rewrite the expression in a more convenient form: 3^7 * (3^2) ^(-2) * (3^4) ^3 * ( 3^5) ^(-2) * 3^6 = 3^7 * 3^(-4) * 3^(12) * 3^(-10) * 3^6 = 3^(7-4+12 -10+6) = 3^(11) . Answer: 3^11. In cases where various grounds, the rule a^n * b^n = (a*b) ^n works for equal indicators. For example, 3^3 * 7^3 = 21^3. Otherwise, when the bases and exponents are different, complete multiplication cannot be performed. Sometimes you can partially simplify or resort to the help of computer technology.

The concept of degree in mathematics is introduced in the 7th grade in algebra class. And subsequently, throughout the entire course of studying mathematics, this concept is actively used in its various forms. Degrees are a rather difficult topic, requiring memorization of values and the ability to count correctly and quickly. To work with degrees faster and better, mathematicians came up with degree properties. They help to reduce large calculations, convert a huge example into a single number to some extent. There are not so many properties, and all of them are easy to remember and apply in practice. Therefore, the article discusses the basic properties of the degree, as well as where they are applied.

Properties of degree

We will look at 12 properties of degrees, including properties of degrees with the same bases, and give an example for each property. Each of these properties will help you solve problems with degrees faster, and will also save you from numerous computational errors.

1st property.

Many people very often forget about this property and make mistakes, representing a number to the zero power as zero.

2nd property.

3rd property.

It must be remembered that this property can only be used when multiplying numbers; it does not work with a sum! And we must not forget that this and the following properties apply only to powers with the same bases.

4th property.

If a number in the denominator is raised to a negative power, then when subtracting, the degree of the denominator is taken in parentheses to correctly change the sign in further calculations.

The property only works when dividing, it does not apply when subtracting!

5th property.

6th property.

This property can also be applied in the opposite direction. A unit divided by a number to some extent is that number to the minus power.

7th property.

This property cannot be applied to sum and difference! Raising a sum or difference to a power uses abbreviated multiplication formulas rather than power properties.

8th property.

9th property.

This property works for any fractional power with a numerator equal to one, the formula will be the same, only the power of the root will change depending on the denominator of the power.

This property is also often used in reverse. The root of any power of a number can be represented as this number to the power of one divided by the power of the root. This property is very useful in cases where the root of a number cannot be extracted.

10th property.

This property works not only with square root and second degree. If the degree of the root and the degree to which this root is raised coincide, then the answer will be a radical expression.

11th property.

You need to be able to see this property in time when solving it in order to save yourself from huge calculations.

12th property.

Each of these properties will come across you more than once in tasks; it can be given in its pure form, or it may require some transformations and the use of other formulas. Therefore for the right decision It’s not enough to know just the properties; you need to practice and incorporate other mathematical knowledge.

Application of degrees and their properties

They are actively used in algebra and geometry. Degrees in mathematics have a separate, important place. With their help, exponential equations and inequalities are solved, and equations and examples related to other branches of mathematics are often complicated by powers. Powers help to avoid large and lengthy calculations; powers are easier to abbreviate and calculate. But to work with large powers, or with powers of large numbers, you need to know not only the properties of the power, but also work competently with bases, be able to expand them to make your task easier. For convenience, you should also know the meaning of numbers raised to a power. This will reduce your time when solving, eliminating the need for lengthy calculations.

The concept of degree plays a special role in logarithms. Since the logarithm, in essence, is a power of a number.

Abbreviated multiplication formulas are another example of the use of powers. The properties of degrees cannot be used in them; they are expanded according to special rules, but in each formula of abbreviated multiplication there are invariably degrees.

Degrees are also actively used in physics and computer science. All conversions to the SI system are made using powers, and in the future, when solving problems, the properties of the power are used. In computer science, powers of two are actively used for the convenience of counting and simplifying the perception of numbers. Further calculations for converting units of measurement or calculations of problems, just like in physics, occur using the properties of degrees.

Degrees are also very useful in astronomy, where you rarely see the use of the properties of a degree, but the degrees themselves are actively used to shorten the notation of various quantities and distances.

Degrees are also used in ordinary life, when calculating areas, volumes, distances.

Degrees are used to record very large and very small quantities in any field of science.

Exponential equations and inequalities

Properties of degrees occupy a special place precisely in exponential equations and inequalities. These tasks are very common, as in school course, and in exams. All of them are solved by applying the properties of degree. The unknown is always found in the degree itself, so knowing all the properties, solving such an equation or inequality is not difficult.

Addition and subtraction of powers

It is obvious that numbers with powers can be added like other quantities , by adding them one after another with their signs.

So, the sum of a 3 and b 2 is a 3 + b 2.
The sum of a 3 - b n and h 5 -d 4 is a 3 - b n + h 5 - d 4.

Odds equal degrees identical variables can be added or subtracted.

So, the sum of 2a 2 and 3a 2 is equal to 5a 2.

It is also obvious that if you take two squares a, or three squares a, or five squares a.

But degrees various variables And various degrees identical variables, must be composed by adding them with their signs.

So, the sum of a 2 and a 3 is the sum of a 2 + a 3.

It is obvious that the square of a, and the cube of a, is not equal to twice the square of a, but to twice the cube of a.

The sum of a 3 b n and 3a 5 b 6 is a 3 b n + 3a 5 b 6.

Subtraction powers are carried out in the same way as addition, except that the signs of the subtrahends must be changed accordingly.

Or:
2a 4 - (-6a 4) = 8a 4
3h 2 b 6 — 4h 2 b 6 = -h 2 b 6
5(a - h) 6 - 2(a - h) 6 = 3(a - h) 6

Multiplying powers

Numbers with powers can be multiplied, like other quantities, by writing them one after the other, with or without a multiplication sign between them.

Thus, the result of multiplying a 3 by b 2 is a 3 b 2 or aaabb.

Or:
x -3 ⋅ a m = a m x -3
3a 6 y 2 ⋅ (-2x) = -6a 6 xy 2
a 2 b 3 y 2 ⋅ a 3 b 2 y = a 2 b 3 y 2 a 3 b 2 y

The result in the last example can be ordered by adding identical variables.
The expression will take the form: a 5 b 5 y 3.

By comparing several numbers (variables) with powers, we can see that if any two of them are multiplied, then the result is a number (variable) with a power equal to amount degrees of terms.

So, a 2 .a 3 = aa.aaa = aaaaa = a 5 .

Here 5 is the power of the multiplication result, which is equal to 2 + 3, the sum of the powers of the terms.

So, a n .a m = a m+n .

For a n , a is taken as a factor as many times as the power of n;

And a m is taken as a factor as many times as the degree m is equal to;

That's why, powers with the same bases can be multiplied by adding the exponents of the powers.

So, a 2 .a 6 = a 2+6 = a 8 . And x 3 .x 2 .x = x 3+2+1 = x 6 .

Or:
4a n ⋅ 2a n = 8a 2n
b 2 y 3 ⋅ b 4 y = b 6 y 4
(b + h - y) n ⋅ (b + h - y) = (b + h - y) n+1

Multiply (x 3 + x 2 y + xy 2 + y 3) ⋅ (x - y).
Answer: x 4 - y 4.
Multiply (x 3 + x – 5) ⋅ (2x 3 + x + 1).

This rule is also true for numbers whose exponents are negative.

1. So, a -2 .a -3 = a -5 . This can be written as (1/aa).(1/aaa) = 1/aaaaa.

2. y -n .y -m = y -n-m .

3. a -n .a m = a m-n .

If a + b are multiplied by a - b, the result will be a 2 - b 2: that is

The result of multiplying the sum or difference of two numbers equal to the sum or the difference of their squares.

If you multiply the sum and difference of two numbers raised to square, the result will be equal to the sum or difference of these numbers in fourth degrees.

So, (a - y).(a + y) = a 2 - y 2.
(a 2 - y 2)⋅(a 2 + y 2) = a 4 - y 4.
(a 4 - y 4)⋅(a 4 + y 4) = a 8 - y 8.

Division of degrees

Numbers with powers can be divided like other numbers, by subtracting from the dividend, or by placing them in fraction form.

Thus, a 3 b 2 divided by b 2 is equal to a 3.

Writing a 5 divided by a 3 looks like $\frac $. But this is equal to a 2 . In a series of numbers
a +4 , a +3 , a +2 , a +1 , a 0 , a -1 , a -2 , a -3 , a -4 .
any number can be divided by another, and the exponent will be equal to difference indicators of divisible numbers.

When dividing degrees with the same base, their exponents are subtracted..

So, y 3:y 2 = y 3-2 = y 1. That is, $\frac = y$.

And a n+1:a = a n+1-1 = a n . That is, $\frac = a^n$.

Or:
y 2m: y m = y m
8a n+m: 4a m = 2a n
12(b + y) n: 3(b + y) 3 = 4(b +y) n-3

The rule is also true for numbers with negative values of degrees.
The result of dividing a -5 by a -3 is a -2.
Also, $\frac: \frac = \frac .\frac = \frac = \frac $.

h 2:h -1 = h 2+1 = h 3 or $h^2:\frac = h^2.\frac = h^3$

It is necessary to master multiplication and division of powers very well, since such operations are very widely used in algebra.

Examples of solving examples with fractions containing numbers with powers

1. Decrease the exponents by $\frac $ Answer: $\frac $.

2. Decrease exponents by $\frac$. Answer: $\frac$ or 2x.

3. Reduce the exponents a 2 /a 3 and a -3 /a -4 and bring to a common denominator.
a 2 .a -4 is a -2 the first numerator.
a 3 .a -3 is a 0 = 1, the second numerator.
a 3 .a -4 is a -1 , the common numerator.
After simplification: a -2 /a -1 and 1/a -1 .

4. Reduce the exponents 2a 4 /5a 3 and 2 /a 4 and bring to a common denominator.
Answer: 2a 3 /5a 7 and 5a 5 /5a 7 or 2a 3 /5a 2 and 5/5a 2.

5. Multiply (a 3 + b)/b 4 by (a - b)/3.

6. Multiply (a 5 + 1)/x 2 by (b 2 - 1)/(x + a).

7. Multiply b 4 /a -2 by h -3 /x and a n /y -3 .

8. Divide a 4 /y 3 by a 3 /y 2 . Answer: a/y.

Properties of degree

We remind you that in this lesson we will understand properties of degrees with natural indicators and zero. Powers with rational exponents and their properties will be discussed in lessons for 8th grade.

A power with a natural exponent has several important properties that allow us to simplify calculations in examples with powers.

A power with a natural exponent has several important properties that allow us to simplify calculations in examples with powers.
Product of powers

When multiplying powers with the same bases, the base remains unchanged, and the exponents of the powers are added.

a m · a n = a m + n, where “a” is any number, and “m”, “n” are any natural numbers.

This property of powers also applies to the product of three or more powers.

Simplify the expression.
b b 2 b 3 b 4 b 5 = b 1 + 2 + 3 + 4 + 5 = b 15
Present it as a degree.
6 15 36 = 6 15 6 2 = 6 15 6 2 = 6 17
Present it as a degree.
(0.8) 3 · (0.8) 12 = (0.8) 3 + 12 = (0.8) 15

Please note that in the specified property we were talking only about the multiplication of powers with the same bases. It does not apply to their addition.

You cannot replace the sum (3 3 + 3 2) with 3 5. This is understandable if
calculate (3 3 + 3 2) = (27 + 9) = 36, and 3 5 = 243

calculate (3 3 + 3 2) = (27 + 9) = 36, and 3 5 = 243
Partial degrees

When dividing powers with the same bases, the base remains unchanged, and the exponent of the divisor is subtracted from the exponent of the dividend.

Write the quotient as a power
(2b) 5: (2b) 3 = (2b) 5 − 3 = (2b) 2
Calculate.

11 3 − 2 4 2 − 1 = 11 4 = 44
Example. Solve the equation. We use the property of quotient powers.
3 8: t = 3 4

Answer: t = 3 4 = 81

Example. Simplify the expression.
4 5m + 6 4 m + 2: 4 4m + 3 = 4 5m + 6 + m + 2: 4 4m + 3 = 4 6m + 8 − 4m − 3 = 4 2m + 5

4 5m + 6 4 m + 2: 4 4m + 3 = 4 5m + 6 + m + 2: 4 4m + 3 = 4 6m + 8 − 4m − 3 = 4 2m + 5

2 11 − 5 = 2 6 = 64

Please note that in Property 2 we were only talking about dividing powers with the same bases.

You cannot replace the difference (4 3 −4 2) with 4 1. This is understandable if you calculate (4 3 −4 2) = (64 − 16) = 48, and 4 1 = 4

Be careful!
Raising a degree to a power

When raising a degree to a power, the base of the degree remains unchanged, and the exponents are multiplied.

(a n) m = a n · m, where “a” is any number, and “m”, “n” are any natural numbers.

We remind you that a quotient can be represented as a fraction. Therefore, we will dwell on the topic of raising a fraction to a power in more detail on the next page.

How to multiply powers

How to multiply powers? Which powers can be multiplied and which cannot? How to multiply a number by a power?

In algebra, you can find a product of powers in two cases:

1) if the degrees have the same bases;

2) if the degrees have the same indicators.

When multiplying powers with the same bases, the base must be left the same, and the exponents must be added:

When multiplying degrees with the same indicators, the overall indicator can be taken out of brackets:

Let's look at how to multiply powers using specific examples.

The unit is not written in the exponent, but when multiplying powers, they take into account:

When multiplying, there can be any number of powers. It should be remembered that you don’t have to write the multiplication sign before the letter:

In expressions, exponentiation is done first.

If you need to multiply a number by a power, you should first perform the exponentiation, and only then the multiplication:

Multiplying powers with the same bases

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In this lesson we will study multiplication of powers with like bases. First, let us recall the definition of degree and formulate a theorem on the validity of the equality . Then we will give examples of its application on specific numbers and prove it. We will also apply the theorem to solve various problems.

Topic: Power with a natural exponent and its properties

Lesson: Multiplying powers with the same bases (formula)

1. Basic definitions

Basic definitions:

n- exponent,

— n th power of a number.

2. Statement of Theorem 1

Theorem 1. For any number A and any natural n And k the equality is true:

In other words: if A– any number; n And k natural numbers, then:

Hence rule 1:

3. Explanatory tasks

Conclusion: special cases confirmed the correctness of Theorem No. 1. Let us prove it in the general case, that is, for any A and any natural n And k.

4. Proof of Theorem 1

Given a number A– any; numbers n And k – natural. Prove:

The proof is based on the definition of degree.

5. Solving examples using Theorem 1

Example 1: Think of it as a degree.

To solve the following examples, we will use Theorem 1.

and)

6. Generalization of Theorem 1

A generalization used here:

7. Solving examples using a generalization of Theorem 1

8. Solving various problems using Theorem 1

Example 2: Calculate (you can use the table of basic powers).

A) (according to the table)

Example 3: Write it as a power with base 2.

Example 4: Determine the sign of the number:

, A - negative, since the exponent at -13 is odd.

Example 5: Replace (·) with a power of a number with a base r:

We have, that is.

9. Summing up

1. Dorofeev G.V., Suvorova S.B., Bunimovich E.A. and others. Algebra 7. 6th edition. M.: Enlightenment. 2010

1. School assistant (Source).

1. Present as a power:

a B C D E)

3. Write as a power with base 2:

4. Determine the sign of the number:

5. Replace (·) with a power of a number with a base r:

a) r 4 · (·) = r 15; b) (·) · r 5 = r 6

Multiplication and division of powers with the same exponents

In this lesson we will study multiplication of powers with equal exponents. First, let's recall the basic definitions and theorems about multiplying and dividing powers with the same bases and raising powers to powers. Then we formulate and prove theorems on multiplication and division of powers with the same exponents. And then with their help we will solve a number of typical problems.

Reminder of basic definitions and theorems

Here a- the basis of the degree,

— n th power of a number.

Theorem 1. For any number A and any natural n And k the equality is true:

When multiplying powers with the same bases, the exponents are added, the base remains unchanged.

Theorem 2. For any number A and any natural n And k, such that n > k the equality is true:

When dividing degrees with the same bases, the exponents are subtracted, but the base remains unchanged.

Theorem 3. For any number A and any natural n And k the equality is true:

All the theorems listed were about powers with the same reasons, in this lesson we will look at degrees with the same indicators.

Examples for multiplying powers with the same exponents

Consider the following examples:

Let's write down the expressions for determining the degree.

Conclusion: From the examples it can be seen that , but this still needs to be proven. Let us formulate the theorem and prove it in the general case, that is, for any A And b and any natural n.

Formulation and proof of Theorem 4

For any numbers A And b and any natural n the equality is true:

Proof Theorem 4 .

By definition of degree:

So we have proven that .

To multiply powers with the same exponents, it is enough to multiply the bases and leave the exponent unchanged.

Formulation and proof of Theorem 5

Let us formulate a theorem for dividing powers with the same exponents.

For any number A And b () and any natural n the equality is true:

Proof Theorem 5 .

Let's write down the definition of degree:

Statement of theorems in words

So, we have proven that .

To divide powers with the same exponents into each other, it is enough to divide one base by another, and leave the exponent unchanged.

Solving typical problems using Theorem 4

Example 1: Present as a product of powers.

To solve the following examples, we will use Theorem 4.

To solve the following example, recall the formulas:

Generalization of Theorem 4

Generalization of Theorem 4:

Solving Examples Using Generalized Theorem 4

Continuing to solve typical problems

Example 2: Write it as a power of the product.

Example 3: Write it as a power with exponent 2.

Calculation examples

Example 4: Calculate in the most rational way.

2. Merzlyak A.G., Polonsky V.B., Yakir M.S. Algebra 7. M.: VENTANA-GRAF

3. Kolyagin Yu.M., Tkacheva M.V., Fedorova N.E. and others. Algebra 7.M.: Enlightenment. 2006

2. School assistant (Source).

1. Present as a product of powers:

A) ; b) ; V) ; G) ;

2. Write as a power of the product:

3. Write as a power with exponent 2:

4. Calculate in the most rational way.

Mathematics lesson on the topic “Multiplication and division of powers”

Sections: Mathematics

Pedagogical goal:

the student will learn distinguish between the properties of multiplication and division of powers with natural exponents; apply these properties in the case of the same bases;

the student will have the opportunity be able to perform transformations of degrees with different bases and be able to perform transformations in combined tasks.

Tasks:

organize students’ work by repeating previously studied material;

ensure the level of reproduction by performing various types of exercises;

organize a check on students’ self-assessment through testing.

Activity units of teaching: determination of degree with a natural indicator; degree components; definition of private; combinational law of multiplication.

I. Organizing a demonstration of students’ mastery of existing knowledge. (step 1)

a) Updating knowledge:

2) Formulate a definition of degree with a natural exponent.

a n =a a a a … a (n times)

b k =b b b b a… b (k times) Justify the answer.

II. Organization of self-assessment of the student’s degree of proficiency in current experience. (step 2)

Self-test: ( individual work in two versions.)

A1) Present the product 7 7 7 7 x x x as a power:

A2) Represent the power (-3) 3 x 2 as a product

A3) Calculate: -2 3 2 + 4 5 3

I select the number of tasks in the test in accordance with the preparation of the class level.

I give you the key to the test for self-test. Criteria: pass - no pass.

III. Educational and practical task (step 3) + step 4. (the students themselves will formulate the properties)

calculate: 2 2 2 3 = ? 3 3 3 2 3 =?

Simplify: a 2 a 20 = ? b 30 b 10 b 15 = ?

While solving problems 1) and 2), students propose a solution, and I, as a teacher, organize the class to find a way to simplify powers when multiplying with the same bases.

Teacher: come up with a way to simplify powers when multiplying with the same bases.

An entry appears on the cluster:

The topic of the lesson is formulated. Multiplication of powers.

Teacher: come up with a rule for dividing powers with the same bases.

Reasoning: what action is used to check division? a 5: a 3 = ? that a 2 a 3 = a 5

I return to the diagram - a cluster and add to the entry - .. when dividing, we subtract and add the topic of the lesson. ...and division of degrees.

IV. Communicating to students the limits of knowledge (as a minimum and as a maximum).

Teacher: the minimum task for today’s lesson is to learn to apply the properties of multiplication and division of powers with the same bases, and the maximum task is to apply multiplication and division together.

We write on the board : a m a n = a m+n ; a m: a n = a m-n

V. Organization of studying new material. (step 5)

a) According to the textbook: No. 403 (a, c, e) tasks with different wordings

No. 404 (a, d, f) independent work, then I organize a mutual check and give the keys.

b) For what value of m is the equality valid? a 16 a m = a 32; x h x 14 = x 28; x 8 (*) = x 14

Assignment: come up with similar examples for division.

c) No. 417 (a), No. 418 (a) Traps for students: x 3 x n = x 3n; 3 4 3 2 = 9 6 ; a 16: a 8 = a 2.

VI. Summarizing what has been learned, conducting diagnostic work (which encourages students, and not the teacher, to study this topic) (step 6)

Diagnostic work.

Test(place the keys on back side test).

Task options: represent the quotient x 15 as a power: x 3; represent as a power the product (-4) 2 (-4) 5 (-4) 7 ; for which m is the equality a 16 a m = a 32 valid? find the value of the expression h 0: h 2 at h = 0.2; calculate the value of the expression (5 2 5 0) : 5 2 .

Lesson summary. Reflection. I divide the class into two groups.

Find arguments in group I: in favor of knowing the properties of the degree, and group II - arguments that will say that you can do without properties. We listen to all the answers and draw conclusions. In subsequent lessons, you can offer statistical data and call the rubric “It’s beyond belief!”

The average person eats 32 10 2 kg of cucumbers during their lifetime.

The wasp is capable of making a non-stop flight of 3.2 10 2 km.

When glass cracks, the crack propagates at a speed of about 5 10 3 km/h.

A frog eats more than 3 tons of mosquitoes in its life. Using the degree, write in kg.

The most prolific is considered to be the ocean fish - the moon (Mola mola), which lays up to 300,000,000 eggs with a diameter of about 1.3 mm in one spawning. Write this number using a power.

VII. Homework.

Historical reference. What numbers are called Fermat numbers.

P.19. No. 403, No. 408, No. 417

Used Books:

Textbook "Algebra-7", authors Yu.N. Makarychev, N.G. Mindyuk et al.

Didactic material for 7th grade, L.V. Kuznetsova, L.I. Zvavich, S.B. Suvorov.

Encyclopedia of mathematics.

Magazine "Kvant".

Properties of degrees, formulations, proofs, examples.

After the power of a number has been determined, it is logical to talk about degree properties. In this article we will give the basic properties of the power of a number, while touching on all possible exponents. Here we will provide proofs of all properties of degrees, and also show how these properties are used when solving examples.

Page navigation.

Properties of degrees with natural exponents

By definition of a power with a natural exponent, the power a n is the product of n factors, each of which is equal to a. Based on this definition, and also using properties of multiplication of real numbers, we can obtain and justify the following properties of degree with natural exponent:

the main property of the degree a m ·a n =a m+n, its generalization a n 1 ·a n 2 ·…·a n k =a n 1 +n 2 +…+n k;

property of quotient powers with identical bases a m:a n =a m−n ;

property of the degree of a product (a·b) n =a n ·b n , its extension (a 1 ·a 2 ·…·a k) n =a 1 n ·a 2 n ·…·a k n ;

property of the quotient to the natural degree (a:b) n =a n:b n ;

raising a degree to a power (a m) n =a m·n, its generalization (((a n 1) n 2) …) n k =a n 1 ·n 2 ·…·n k;

comparison of degree with zero:

if a>0, then a n>0 for any natural number n;
if a=0, then a n =0;
if a 2·m >0 , if a 2·m−1 n ;
if m and n are natural numbers such that m>n, then for 0m n, and for a>0 the inequality a m >a n is true.

Let us immediately note that all written equalities are identical subject to the specified conditions, both their right and left parts can be swapped. For example, the main property of the fraction a m ·a n =a m+n with simplifying expressions often used in the form a m+n =a m ·a n .

Now let's look at each of them in detail.

Let's start with the property of the product of two powers with the same bases, which is called the main property of the degree: for any real number a and any natural numbers m and n, the equality a m ·a n =a m+n is true.

Let us prove the main property of the degree. By the definition of a power with a natural exponent, the product of powers with identical bases of the form a m ·a n can be written as the product . Due to the properties of multiplication, the resulting expression can be written as , and this product is a power of the number a with a natural exponent m+n, that is, a m+n. This completes the proof.

Let us give an example confirming the main property of the degree. Let's take degrees with the same bases 2 and natural powers 2 and 3, using the basic property of degrees we can write the equality 2 2 ·2 3 =2 2+3 =2 5. Let's check its validity by calculating the values of the expressions 2 2 · 2 3 and 2 5 . Carrying out exponentiation, we have 2 2 2 3 =(2 2) (2 2 2) = 4 8 = 32 and 2 5 =2 2 2 2 2 = 32 , since we get equal values, then the equality 2 2 ·2 3 =2 5 is correct, and it confirms the main property of the degree.

The basic property of a degree based on the properties of multiplication can be generalized to the product of three and more degrees with the same bases and natural indicators. So for any number k of natural numbers n 1 , n 2 , …, n k the equality a n 1 ·a n 2 ·…·a n k =a n 1 +n 2 +…+n k is true.

For example, (2,1) 3 ·(2,1) 3 ·(2,1) 4 ·(2,1) 7 = (2,1) 3+3+4+7 =(2,1) 17.

We can move on to the next property of powers with a natural exponent – property of quotient powers with the same bases: for any non-zero real number a and arbitrary natural numbers m and n satisfying the condition m>n, the equality a m:a n =a m−n is true.

Before giving a proof of this property, let us discuss the meaning additional conditions in the wording. The condition a≠0 is necessary in order to avoid division by zero, since 0 n =0, and when we got acquainted with division, we agreed that we cannot divide by zero. The condition m>n is introduced so that we do not go beyond the natural exponents. Indeed, for m>n the exponent a m−n is a natural number, otherwise it will be either zero (which happens for m−n) or a negative number (which happens for m m−n ·a n =a (m−n) +n =a m. From the resulting equality a m−n ·a n =a m and from the connection between multiplication and division it follows that a m−n is a quotient of powers a m and a n. This proves the property of quotients of powers with the same bases.

Let's give an example. Let's take two degrees with the same bases π and natural exponents 5 and 2, the equality π 5:π 2 =π 5−3 =π 3 corresponds to the considered property of the degree.

Now let's consider product power property: natural degree The n product of any two real numbers a and b is equal to the product of the powers a n and b n , that is, (a·b) n =a n ·b n .

Indeed, by the definition of a degree with a natural exponent we have . Last piece based on the properties of multiplication can be rewritten as , which is equal to a n · b n .

Here's an example: .

This property extends to the power of the product of three or more factors. That is, the property of natural degree n of a product of k factors is written as (a 1 ·a 2 ·…·a k) n =a 1 n ·a 2 n ·…·a k n .

For clarity, we will show this property with an example. For the product of three factors to the power of 7 we have .

The following property is property of a quotient in kind: the quotient of real numbers a and b, b≠0 to the natural power n is equal to the quotient of powers a n and b n, that is, (a:b) n =a n:b n.

The proof can be carried out using the previous property. So (a:b) n ·b n =((a:b)·b) n =a n , and from the equality (a:b) n ·b n =a n it follows that (a:b) n is the quotient of division a n on bn.

Let's write this property using specific numbers as an example: .

Now let's voice it property of raising a power to a power: for any real number a and any natural numbers m and n, the power of a m to the power of n is equal to the power of the number a with exponent m·n, that is, (a m) n =a m·n.

For example, (5 2) 3 =5 2·3 =5 6.

The proof of the power-to-degree property is the following chain of equalities: .

The property considered can be extended to degree to degree to degree, etc. For example, for any natural numbers p, q, r and s, the equality . For greater clarity, let's give an example with specific numbers: (((5,2) 3) 2) 5 =(5,2) 3+2+5 =(5,2) 10.

It remains to dwell on the properties of comparing degrees with a natural exponent.

Let's start by proving the property of comparing zero and power with a natural exponent.

First, let's prove that a n >0 for any a>0.

The product of two positive numbers is a positive number, as follows from the definition of multiplication. This fact and the properties of multiplication suggest that the result of multiplying any number of positive numbers will also be a positive number. And the power of a number a with natural exponent n, by definition, is the product of n factors, each of which is equal to a. These arguments allow us to assert that for any positive base a, the degree a n is a positive number. Due to the proven property 3 5 >0, (0.00201) 2 >0 and .

It is quite obvious that for any natural number n with a=0 the degree of a n is zero. Indeed, 0 n =0·0·…·0=0 . For example, 0 3 =0 and 0 762 =0.

Let's move on to negative bases of degree.

Let's start with the case when the exponent is an even number, let's denote it as 2·m, where m is a natural number. Then . According to the rule for multiplying negative numbers, each of the products of the form a·a is equal to the product of the absolute values of the numbers a and a, which means that it is a positive number. Therefore, the product will also be positive and degree a 2·m. Let's give examples: (−6) 4 >0 , (−2,2) 12 >0 and .

Finally, when the base a is a negative number and the exponent is an odd number 2 m−1, then . All products a·a are positive numbers, the product of these positive numbers is also positive, and its multiplication by the remaining negative number a results in a negative number. Due to this property (−5) 3 17 n n is the product of the left and right sides of n true inequalities a properties of inequalities, a provable inequality of the form a n n is also true. For example, due to this property, the inequalities 3 7 7 and .

It remains to prove the last of the listed properties of powers with natural exponents. Let's formulate it. Of two powers with natural exponents and identical positive bases less than one, the one whose exponent is smaller is greater; and of two powers with natural exponents and identical bases greater than one, the one whose exponent is greater is greater. Let us proceed to the proof of this property.

Let us prove that for m>n and 0m n . To do this, we write down the difference a m − a n and compare it with zero. The recorded difference, after taking a n out of brackets, will take the form a n ·(a m−n−1) . The resulting product is negative as the product of a positive number a n and a negative number a m−n −1 (a n is positive as the natural power of a positive number, and the difference a m−n −1 is negative, since m−n>0 due to the initial condition m>n, whence it follows that when 0m−n is less than unity). Therefore, a m −a n m n , which is what needed to be proven. As an example, we give the correct inequality.

It remains to prove the second part of the property. Let us prove that for m>n and a>1 a m >a n is true. The difference a m −a n after taking a n out of brackets takes the form a n ·(a m−n −1) . This product is positive, since for a>1 the degree a n is a positive number, and the difference a m−n −1 is a positive number, since m−n>0 due to the initial condition, and for a>1 the degree a m−n is greater than one . Consequently, a m −a n >0 and a m >a n , which is what needed to be proven. This property is illustrated by the inequality 3 7 >3 2.

Properties of powers with integer exponents

Since they are whole positive numbers there are natural numbers, then all the properties of powers with positive integer exponents coincide exactly with the properties of powers with natural exponents listed and proven in the previous paragraph.

We defined a degree with an integer negative exponent, as well as a degree with a zero exponent, in such a way that all properties of degrees with natural exponents, expressed by equalities, remained valid. Therefore, all these properties are valid for both zero exponents and negative exponents, while, of course, the bases of the powers are different from zero.

So, for any real and non-zero numbers a and b, as well as any integers m and n, the following are true: properties of powers with integer exponents:

a m ·a n =a m+n ;
a m:a n =a m−n ;
(a·b) n =a n ·b n ;
(a:b) n =a n:b n ;
(a m) n =a m·n ;
if n is a positive integer, a and b are positive numbers, and a n n and a −n >b −n ;
if m and n are integers, and m>n, then for 0m n, and for a>1 the inequality a m >a n holds.

When a=0, the powers a m and a n make sense only when both m and n are positive integers, that is, natural numbers. Thus, the properties just written are also valid for the cases when a=0 and the numbers m and n are positive integers.

Proving each of these properties is not difficult; to do this, it is enough to use the definitions of degrees with natural and integer exponents, as well as the properties of operations with real numbers. As an example, let us prove that the power-to-power property holds for both positive integers and non-positive integers. To do this, you need to show that if p is zero or a natural number and q is zero or a natural number, then the equalities (a p) q =a p·q, (a −p) q =a (−p)·q, (a p ) −q =a p·(−q) and (a −p) −q =a (−p)·(−q) . Let's do it.

For positive p and q, the equality (a p) q =a p·q was proven in the previous paragraph. If p=0, then we have (a 0) q =1 q =1 and a 0·q =a 0 =1, whence (a 0) q =a 0·q. Similarly, if q=0, then (a p) 0 =1 and a p·0 =a 0 =1, whence (a p) 0 =a p·0. If both p=0 and q=0, then (a 0) 0 =1 0 =1 and a 0·0 =a 0 =1, whence (a 0) 0 =a 0·0.

Now we prove that (a −p) q =a (−p)·q . By definition of a power with a negative integer exponent, then . By the property of quotients to powers we have . Since 1 p =1·1·…·1=1 and , then . The last expression, by definition, is a power of the form a −(p·q), which, due to the rules of multiplication, can be written as a (−p)·q.

Likewise .

AND .

Using the same principle, you can prove all other properties of a degree with an integer exponent, written in the form of equalities.

In the penultimate of the recorded properties, it is worth dwelling on the proof of the inequality a −n >b −n, which is valid for any negative integer −n and any positive a and bfor which the condition a is satisfied . Let us write down and transform the difference between the left and right sides of this inequality: . Since by condition a n n , therefore, b n −a n >0 . The product a n · b n is also positive as the product of positive numbers a n and b n . Then the resulting fraction is positive as the quotient of the positive numbers b n −a n and a n ·b n . Therefore, whence a −n >b −n , which is what needed to be proved.

The last property of powers with integer exponents is proved in the same way as a similar property of powers with natural exponents.

Properties of powers with rational exponents

We defined a degree with a fractional exponent by extending the properties of a degree with an integer exponent to it. In other words, powers with fractional exponents have the same properties as powers with integer exponents. Namely:

property of the product of powers with the same bases for a>0, and if and, then for a≥0;
property of quotient powers with the same bases for a>0 ;
property of a product to a fractional power for a>0 and b>0, and if and, then for a≥0 and (or) b≥0;
property of a quotient to a fractional power for a>0 and b>0, and if , then for a≥0 and b>0;
property of degree to degree for a>0, and if and, then for a≥0;
property of comparing powers with equal rational exponents: for any positive numbers a and b, a 0 the inequality a p p is true, and for p p >b p ;
the property of comparing powers with rational exponents and equal bases: for rational numbers p and q, p>q for 0p q, and for a>0 – inequality a p >a q.

The proof of the properties of powers with fractional exponents is based on the definition of a power with a fractional exponent, on the properties of the arithmetic root of the nth degree and on the properties of a power with an integer exponent. Let us provide evidence.

By definition of a power with a fractional exponent and , then . The properties of the arithmetic root allow us to write the following equalities. Further, using the property of a degree with an integer exponent, we obtain , from which, by the definition of a degree with a fractional exponent, we have , and the indicator of the degree obtained can be transformed as follows: . This completes the proof.

The second property of powers with fractional exponents is proved in an absolutely similar way:

The remaining equalities are proved using similar principles:

Let's move on to proving the next property. Let us prove that for any positive a and b, a 0 the inequality a p p is true, and for p p >b p . Let's write the rational number p as m/n, where m is an integer and n is a natural number. The conditions p 0 in this case will be equivalent to the conditions m 0, respectively. For m>0 and am m . From this inequality, by the property of roots, we have, and since a and b are positive numbers, then, based on the definition of a degree with a fractional exponent, the resulting inequality can be rewritten as, that is, a p p .

Similarly, for m m >b m , whence, that is, a p >b p .

It remains to prove the last of the listed properties. Let us prove that for rational numbers p and q, p>q for 0p q, and for a>0 – the inequality a p >a q. We can always reduce rational numbers p and q to a common denominator, even if we get ordinary fractions and , where m 1 and m 2 are integers, and n is a natural number. In this case, the condition p>q will correspond to the condition m 1 >m 2, which follows from the comparison rule ordinary fractions with the same denominators. Then, by the property of comparing degrees with the same bases and natural exponents, for 0m 1 m 2, and for a>1, the inequality a m 1 >a m 2. These inequalities in the properties of the roots can be rewritten accordingly as And . And the definition of a degree with a rational exponent allows us to move on to inequalities and, accordingly. From here we draw the final conclusion: for p>q and 0p q , and for a>0 – the inequality a p >a q .

Properties of powers with irrational exponents

From the way a degree with an irrational exponent is defined, we can conclude that it has all the properties of degrees with rational exponents. So for any a>0 , b>0 and irrational numbers p and q are as follows properties of powers with irrational exponents:

a p ·a q =a p+q ;
a p:a q =a p−q ;
(a·b) p =a p ·b p ;
(a:b) p =a p:b p ;
(a p) q =a p·q ;
for any positive numbers a and b, a 0 the inequality a p p is true, and for p p >b p ;
for irrational numbers p and q, p>q for 0p q, and for a>0 – the inequality a p >a q.

From this we can conclude that powers with any real exponents p and q for a>0 have the same properties.

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The rule for dividing degrees. When dividing powers with the same base, the base is left the same, and the exponent of the divisor is subtracted from the exponent of the dividend. Examples:

Slide 11 from the presentation “Division and multiplication of powers” for algebra lessons on the topic “Degree”

Dimensions: 960 x 720 pixels, format: jpg. To download a free slide for use in an algebra lesson, right-click on the image and click “Save Image As.” " You can download the entire presentation “Division and multiplication of powers.ppt” in a zip archive of 1313 KB in size.

“Division and multiplication of powers” - a2 a3 = a2+3 = a5. a3 = a · a · a. Let's find the product of a2 and a3. 100. 2+3. 5 times. 64 = 144 = 1 0000 =. Multiplication and division of powers. 3 times. a2 a3 =.

“Powers of two” - 1024+. Rules for converting from one number system to another. Guselnikova E.V. School No. 130. Content. Table of powers of two. Let's convert the number 1998 from decimal to binary. Kislykh V.N. 11E Zinko K.O. 11F. Teacher: Completed: Let's look at the conversion scheme using an example.

“Degree with a negative exponent” - Degree with a negative exponent. 5 12?3 (27?3). -2. -1. Calculate: -3.

“A power with a rational exponent” - on the topic: “A power with a rational exponent.” Lesson objectives: I. Organizational part. Examination homework 1. Mathematical dictation 2. Peer testing III. Independent work IV. General lesson. During the classes. Preparing for test work V. Summing up the lesson VI. II.

“Power with an integer exponent”—Render the expression as a power. X-12. Arrange in descending order. Express the expression x-12 as the product of two powers with base x if one factor is known. Calculate. Simplify.

“Properties of a degree” - Generalization of knowledge and skills in applying the properties of a degree with a natural indicator. Computational pause. Properties of a degree with a natural exponent. Check yourself! Application of knowledge to solve problems of varying complexity. Test. Physical exercise. Development of perseverance, mental activity and creative activity.

Rule for dividing powers

1. The degree of the product of two or more factors is equal to the product of the degrees of these factors (with the same exponent):

(abc…) n = a n b n c n …

Example 1. (7 2 10) 2 = 7 2 2 2 10 2 = 49 4 100 = 19600. Example 2. (x 2 –a 2) 3 = [(x +a)(x – a)] 3 =( x +a) 3 (x - a) 3

In practice, the reverse conversion is more important:

a n b n c n … = (abc…) n

those. the product of identical powers of several quantities is equal to the same power of the product of these quantities.

Example 3. Example 4. (a +b) 2 (a 2 – ab +b 2) 2 =[(a +b)(a 2 – ab +b 2)] 2 =(a 3 +b 3) 2

2. The power of a quotient (fraction) is equal to the quotient of dividing the same power of the divisor by the same power:

Example 5. Example 6.

Reverse conversion:. Example 7. . Example 8. .

3. When multiplying degrees with the same bases, the exponents of the degrees are added:

Example 9.2 2 2 5 =2 2+5 =2 7 =128. Example 10. (a – 4c +x) 2 (a – 4c +x) 3 =(a – 4c + x) 5.

4. When dividing powers with the same bases, the exponent of the divisor is subtracted from the exponent of the dividend

Example 11. 12 5:12 3 =12 5-3 =12 2 =144. Example 12. (x-y) 3:(x-y) 2 =x-y.

5. When raising a degree to a power, the exponents are multiplied:

Example 13. (2 3) 2 =2 6 =64. Example 14.

Addition, subtraction, multiplication, and division of powers

Addition and subtraction of powers

It is obvious that numbers with powers can be added like other quantities , by adding them one after another with their signs.

So, the sum of a 3 and b 2 is a 3 + b 2.
The sum of a 3 - b n and h 5 -d 4 is a 3 - b n + h 5 - d 4.

Odds equal powers of identical variables can be added or subtracted.