# EXAMPLE 1 Multiplying Integers

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EXAMPLE 1 Multiplying Integers
Diving A diver is swimming downward to explore a coral reef. The diver’s depth is changing by –2 feet per second. The diver started at sea level. What is the diver’s position relative to sea level after 10 seconds? after 30 seconds? SOLUTION a. To find the diver’s position relative to sea level after 10 seconds, use the distance formula d = rt. d = rt Write the distance formula. d = –2 (10) Substitute –2 for r and 10 for t. d = –20 Different signs, so product is negative.

The diver’s position relative to sea level is –20 feet. ANSWER
EXAMPLE 1 Multiplying Integers The diver’s position relative to sea level is –20 feet. ANSWER b. Find the diver’s position relative to sea level after 30 seconds. d = rt Write the distance formula. d (30) –2 = Substitute –2 for r and 30 for t. d = – 60 Different signs, so product is negative. ANSWER The diver’s position relative to sea level is –60 feet.

Multiplying Two or More Integers
EXAMPLE 2 Multiplying Two or More Integers a. –1(6) = –6 Different signs, so product is negative. b. –8(–2) = 16 Same sign, so product is positive. c. –15(0) = 0 Product of an integer and 0 is 0. d. 4(–10)(–12) = –40(–12) Multiply from left to right. = 480 Multiply.

Evaluating an Expression with Integers
EXAMPLE 3 Evaluating an Expression with Integers Evaluate a2 + 3b when a = –5 and b = –11. SOLUTION + 3b a2 + 3(–11) = (–5)2 Substitute –5 for a and –11 for b. = (–11) Evaluate the power. = (–33) Multiply. = –8 Add.

The diver’s position relative to sea level is –26 feet. ANSWER
GUIDED PRACTICE for Examples 1, 2 and 3 1. What If? In Example 1, what is the diver’s position relative to sea level after 13 seconds? SOLUTION To find the diver’s position relative to sea level after 13 seconds, use the distance formula d = rt. d = rt Write the distance formula. d = –2 (13) Substitute –2 for r and 13 for t. d = –26 Different signs, so product is negative. The diver’s position relative to sea level is –26 feet. ANSWER

GUIDED PRACTICE for Examples 1, 2 and 3 Find the product. 2. –1(4)
2. –1(4) = –4 Different signs, so product is negative. (0) = 0 Product of an integer and 0 is 0. 4. –6(–11) = 66 Same sign, so product is positive. 5. –1(–12)(–9) = 12(–9) Multiply from left to right. = –108 Multiply.

Evaluate the expression when a = 3, b = –4, and c = –8 .
GUIDED PRACTICE for Examples 1, 2 and 3 Evaluate the expression when a = 3, b = –4, and c = –8 . 6. ac – b = 3(–8) – (–4) Substitute 3 for a , –4 for b and –8 for c. = (–24) – (–4) Multiply. = –20 Subtract. Substitute 3 for a , –4 for b and –8 for c. 7. ac + b = 3(–8) + (–4) = (–24) + (–4) Multiply. = –28 Add.

Evaluate the expression when a = 3, b = –4, and c = –8 .
GUIDED PRACTICE for Examples 1, 2 and 3 Evaluate the expression when a = 3, b = –4, and c = –8 . + bc 8 a2 . + (–4) (–8) = (3)2 Substitute 3 for a , –4 for b and –8 for c. = 9 + (–4)(–8) Evaluate the power. = Multiply. = 41 Add.

Evaluate the expression when a = 3, b = –4, and c = –8 .
GUIDED PRACTICE for Examples 1, 2 and 3 Evaluate the expression when a = 3, b = –4, and c = –8 . 9 ab – c2 . = 3(–4) – (–8)2 Substitute 3 for a , –4 for b and –8 for c. = 3(–4) – 64 Evaluate the power. = (–12) – 64 Multiply. = –76 Subtract.