1-4 Powers and Exponents Warm Up Lesson Presentation Lesson Quiz Holt Algebra 1 Warm Up Lesson Presentation Lesson Quiz

Warm Up Simplify. 1. 2(2) 2. (–2)(–2) 3. (–2)(–2)(–2) 4 4. 3(3)(3) 4 –8 27 4 9 5.

Objective Evaluate expressions containing exponents.

Vocabulary power base exponent

A power is an expression written with an exponent and a base or the value of such an expression. 3² is an example of a power. The base is the number that is used as a factor. 3 2 The exponent, 2 tells how many times the base, 3, is used as a factor.

When a number is raised to the second power, we usually say it is “squared.” The area of a square is s  s = s2, is the side length. S When a number is raised to the third power, we usually say its “cubed.” The of volume of a cube is s  s  s = s3 is the side length. S

Example 1A: Writing Powers for Geometric Models Write the power represented by the geometric model. The figure is 5 units long, 5 units wide, and 5 units tall. 5  5  5 5 53 The factor 5 is used 3 times.

Example 1B: Writing Powers for Geometric Models Write the power represented by the geometric model. 6 The figure is 6 units long and 6 units wide. 6 x 6 6 62 The factor 6 is used 2 times.

Check It Out! Example 1 Write the power represented by each geometric model. a. The figure is 2 units long and 2 units wide. 2  2 22 The factor 2 is used 2 times. x b. The figure is x units long, x units wide, and x units tall. x  x  x The factor x is used 3 times. x3

There are no easy geometric models for numbers raised to exponents greater than 3, but you can still write them using repeated multiplication or a base and exponent. Reading Exponents Words Multiplication Power Value 3 to the first power 3 31 3 3 to the second power, or 3 squared 3  3 32 9 3 to the third power, or 3 cubed 3  3  3 33 27 3 to the fourth power 34 3  3  3  3 81 3 to the fifth power 3  3  3  3  3 35 243

Caution! In the expression –52, 5 is the base because the negative sign is not in parentheses. In the expression (–2), –2 is the base because of the parentheses.

Example 2: Evaluating Powers Evaluate each expression. A. (–6)3 (–6)(–6)(–6) Use –6 as a factor 3 times. –216 B. –102 Think of a negative sign in front of a power as multiplying by a –1. –1 • 10 • 10 Find the product of –1 and two 10’s. –100

Example 2: Evaluating Powers Evaluate the expression. C. 2 9  Use as a factor 2 times. 2 9 = 4 81 2 9 

Check It Out! Example 2 Evaluate each expression. a. (–5)3 (–5)(–5)(–5) Use –5 as a factor 3 times. –125 b. –62 Think of a negative sign in front of a power as multiplying by –1. –1  6  6 Find the product of –1 and two 6’s. –36

Check It Out! Example 2 Evaluate the expression. c. Use as a factor 3 times. 3 4 27 64

Example 3: Writing Powers Write each number as a power of the given base. A. 64; base 8 8  8 The product of two 8’s is 64. 82 B. 81; base –3 (–3)(–3)(–3)(–3) The product of four –3’s is 81. (–3)4

Check It Out! Example 3 Write each number as a power of a given base. a. 64; base 4 4  4  4 The product of three 4’s is 64. 43 b. –27; base –3 (–3)(–3)(–3) The product of three (–3)’s is –27. –33

Example 4: Problem-Solving Application In case of a school closing, the PTA president calls 3 families. Each of these families calls 3 other families and so on. How many families will have been called in the 4th round of calls? Understand the problem 1 The answer will be the number of families contacted in the 4th round of calls. List the important information: • The PTA president calls 3 families. • Each family then calls 3 more families.

Example 4 Continued 2 Make a Plan Draw a diagram to show the number of Families called in each round of calls. PTA President 1st round of calls 2nd round of calls

Notice that after each round of calls the Example 4 Continued Solve 3 Notice that after each round of calls the number of families contacted is a power of 3. 1st round of calls: 1  3 = 3 or 31 families contacted 2nd round of calls: 3  3 = 9 or 32 families contacted 3rd round of calls: 9  3 = 27 or 33 families contacted So, in the 4th round of calls, 34 families will have been contacted. 34 = 3  3  3  3 = 81 Multiply four 3’s. In the fourth round of calls, 81 families will have been contacted.

Example 4 Continued Look Back 4 Drawing a diagram helps you visualize the problem, but the numbers become too large for a diagram. The diagram helps you recognize the pattern of multiplying by 3 so that you can write the number as a power of 3.

Check it Out! Example 4 What if…? How many bacteria will be on the slide after 8 hours? After each hour, the number of bacteria is a power of 2. 28 2  2  2  2  2  2  2  2 Multiply eight 2’s. 256 The product of eight 2’s.

n n Lesson Quiz 1. Write the power represented by the geometric model. Simplify each expression. 3. –63 −216 2. 4. 6 216 5. (–2)6 64 Write each number as a power of the given base. 6. 343; base 7 73 7. 10,000; base 10 104