Big Ideas Math: Modeling Real Life, Grade 8
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4. Zero and Negative Exponents
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Exercise 16 Page 339

Evaluate each expression. Remember the definition of negative exponents.

Which Is Different? Write (-3)*(-3)*(-3) as a power with an integer base.
Answers: See solution.

Practice makes perfect

Let's take a look at the given questions.

In each of them we will need to use powers. To see which one is different let's analyze each question one at a time. Let's start with the first question.

First Question

First we can write the product in the denominator as a power.
1/3*3*3
1/3^3
Next we will use the definition of a negative exponent.
1/3^3
3^(-3)
The answer to this question is 3^(-3).

Second Question

We want to write 3 to the negative third. This means that we have a power with base 3 and exponent of - 3. 3^(- 3)

Third Question

This time we want to write 13 cubed as a power with an integer base. First let's raise 13 to the power of 3.
(1/3)^3
1^3/3^3
1/3^3
Next, let's use the definition of a negative exponent.
1/3^3
3^(-3)
The answer to this question is 3^(-3).

Fourth Question

Finally, we want to write (-3)*(-3)*(-3) as a power with an integer base. We can do this using the definition of a power.
(-3)*(-3)*(-3)
(-3)^3
The answer to this question is (-3)^3.

Conclusion

Let's compare the answers to all questions.

Question Answer
Write 13*3*3 using a negative exponent. 3^(-3)
Write 3 to the negative third. 3^(-3)
Write 13 cubed as a power with an integer base. 3^(-3)
Write (-3)*(-3)*(-3) as a power with an integer base. ( -3)^3

We can see that the last question is different because it has a different answer.