Envision Math 2.0: Grade 8, Volume 1
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7. More Properties of Integer Exponents
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Exercise 17 Page 50

Practice makes perfect

We are asked to evaluate the following expressions. (-3)^(-8) and-3^(-8) To do this we will use the Negative Exponent Property.

Negative Exponent Property

If a is a non-zero real number, then the following equation is true. a^(- n)=1/a^n

First, let's use this property to evaluate (-3)^(-8). (-3)^(-8)=1/(-3)^8 To simplify this, we can use the Power of Products Property.
1/(-3)^8
1/(-3)^(2*4)
1/((-3)^2)^4
1/(3^2)^4
1/(9)^4
1/9*9*9*9
1/6561
We found that (-3)^(-8) is equal to 16561. Next, let's evaluate the second expression -3^8. We will use the Negative Exponent Property again. -3^(-8)=-1/3^8 To simplify this we can once again use the Power of Products Property.
-1/3^8
-1/3^(2*4)
-1/(3^2)^4
â–Ľ
Simplify
-1/(9)^4
-1/9*9*9*9
-1/6561
We evaluated both expressions. Let's summarize our results.
Expression Evaluation
(-3)^(-8) 1/6561
-3^(-8) -1/6561

This time we will evaluate the following expressions. (-3)^(-9) and-3^(-9) Like in the previous part, we will use the Negative Exponent Property.

Negative Exponent Property

If a is a non-zero real number, then the following equation is true. a^(- n)=1/a^n

First, let's use this property to evaluate (-3)^(-9). (-3)^(-9)=1/(-3)^9 To simplify this, we can use the Power of Products Property.
1/(-3)^9
1/(-3)^(3*3)
1/((-3)^3)^3

a^3=a* a* a

1/((-3)(-3)(-3))^3
1/(-27)^3

a^3=a* a* a

1/(-27)(-27)(-27)
1/-19 683
-1/19 683
We found that (-3)^(-9) is equal to - 119 683. Next let's evaluate the second expression, -3^9. We will use the Negative Exponent Property again. -3^(-9)=-1/3^9 To simplify this we can once again use the Power of Products Property.
-1/3^9
-1/3^(3*3)
-1/(3^3)^3
â–Ľ
Simplify

a^3=a* a* a

-1/(3*3*3)^3
-1/(27)^3

a^3=a* a* a

-1/27*27*27
-1/19 683
We evaluated both expressions. Let's summarize our results.
Expression Evaluation
(-3)^(-9) -1/19 683
-3^(-9) -1/19 683

The expressions turned out to be equal!