1. Warm Up
Evaluate each expression for the given values of the variables.
1. x3y2 for x = –1 and y = 10
for x = 4 and y = (–7)
Write each number as a power of the given base.
–100
3. 64; base 4 43
4. –27; base (–3)
(–3)3

2. Objectives Evaluate expressions containing zero and integer exponents.
Simplify expressions containing zero and integer exponents.

3. You have seen positive exponents
You have seen positive exponents. Recall that to simplify 32, use 3 as a factor 2 times: 32 = 3  3 = 9.
But what does it mean for an exponent to be negative or 0? You can use a table and look for a pattern to figure it out.
Power
Value 55 54 53 52 51 50
5–1
5–2
3125
625
125 25 5
 5
 5
 5
 5

4. When the exponent decreases by one, the value of the power is divided by 5. Continue the pattern of dividing by 5.

5. Base x
Exponent
Remember! 4

7. Notice the phrase “nonzero number” in the previous table
Notice the phrase “nonzero number” in the previous table. This is because 00 and 0 raised to a negative power are both undefined. For example, if you use the pattern given above the table with a base of 0 instead of 5, you would get 0º = . Also 0–6 would be = . Since division by 0 is undefined, neither value exists.

8. 2–4 is read “2 to the negative fourth power.”
Reading Math

9. Example 1: Application
One cup is 2–4 gallons. Simplify this expression.
cup is equal to

10. Check It Out! Example 1
A sand fly may have a wingspan up to 5–3 m. Simplify this expression.
5-3 m is equal to

11. Example 2: Zero and Negative Exponents
Simplify.
A. 4–3
B. 70
Any nonzero number raised to the zero power is 1.
7º = 1
C. (–5)–4
D. –5–4

12. In (–3)–4, the base is negative because the negative sign is inside the parentheses. In –3–4 the base (3) is positive.
Caution

13. Example 3A: Evaluating Expressions with Zero and Negative Exponents
Evaluate the expression for the given value of the variables.
x–2 for x = 4
Substitute 4 for x.
Use the definition

14. Check It Out! Example 3a
Evaluate the expression for the given value of the variable.
p–3 for p = 4
Substitute 4 for p.
Evaluate exponent.
Write the power in the denominator as a product.
Evaluate the powers in the product.

15. Example 3B: Evaluating Expressions with Zero and Negative Exponents
Evaluate the expression for the given values of the variables.
–2a0b-4 for a = 5 and b = –3
Substitute 5 for a and –3 for b.
Evaluate expressions with exponents.
Write the power in the denominator as a product.
Evaluate the powers in the product.
Simplify.

16. Check It Out! Example 3b
Evaluate the expression for the given values of the variables.
for a = –2 and b = 6
Substitute –2 for a and 6 for b.
Evaluate expressions with exponents.
Write the power in the denominator as a product.
Evaluate the powers in the product. 2
Simplify.

17. What if you have an expression with a negative exponent in a denominator, such as ?
Definition of a negative exponent.
Substitute –8 for n.
Simplify the exponent on the right side.
An expression that contains negative or zero exponents is not considered to be simplified. Expressions should be rewritten with only positive exponents.
So if a base with a negative exponent is in a denominator, it is equivalent to the same base with the opposite (positive) exponent in the numerator.

18. Example 4: Simplifying Expressions with Zero and Negative Numbers
A. 7w–4

19. Example 4: Simplifying Expressions with Zero and Negative NumbersC.
and

20. Check It Out! Example 4
Simplify.
a. 2r0m–3
rº = 1 and b. c.

21. Lesson Quiz: Part I
Simplify.
2. 2–6
3. (–7)–3
4. 60
5. –112

22. Lesson Quiz: Part II
Evaluate each expression for the given value(s) of the variables(s). 6.
x–4 for x =10 7.
for a = 6 and b = 3