Page 157 - Basic College Mathematics with Early Integers

134 C HAPTE R 2 I INTEGERS AND INTRODUCTION TO VARIABLES

To visualize subtraction, try the following:
The difference between 5°F and -2°F can be found by 5 F
subtracting.That is,
7 degrees
5 - 1-22 = 5 + 2 = 7
0 F
Can you visually see from the thermometer on the right that 2 F
there are actually 7 degrees between 5°F and -2°F?

Concept Check What is wrong with the following calculation?
-9 - 1-62 =-15

PRACTICE 8 Example 8 Subtract 7 from -3.
Subtract 5 from -10.
Solution: To subtract 7 from -3, we find

-3 - 7 =-3 + 1-72 =-10
Work Practice 8

Objective Adding and Subtracting Integers
If a problem involves adding or subtracting more than two integers, we rewrite dif-
ferences as sums and add. Recall that by associative and commutative properties, we
may add numbers in any order. In Examples 9 and 10, we will add from left to right.

PRACTICE 9 Example 9 Simplify: 7 - 8 - 1-52 - 1
Simplify: -4 - 3 - 7 - 1-52
Solution: 7 - 8 - 1-52 - 1 = 7 + 1-82 + 5 + 1-12
(')'*
= -1 + 5 + 1-12
('')''*
= 4 + 1-12
('')''*
= 3
Work Practice 9
PRACTICE 10 Example 10 Simplify: 7 + 1-122 - 3 - 1-82
Simplify:
Solution: 7 + 1-122 - 3 - 1-82 = 7 + 1-122 + 1-32 + 8
3 + 1-52 - 6 - 1-42
e
= -5 + 1-32 + 8
g
= -8 w + 8
= 0
Work Practice 10
Objective Evaluating Expressions

Now let’s practice evaluating expressions when the replacement values are integers.

PRACTICE 11 Example 11 Evaluate x - y for x =-3 and y = 9.
Evaluate x - y for x =-2 and
y = 14. Solution: Replace x with -3 and y with 9 in x - y.
x - y
Answers T T T Copyright 2012 Pearson Education, Inc.
= 1-32 - 9
8. -15 9. -9 10. -4 11. -16
= 1-32 + 1-92
Concept Check Answer =-12
-9 - 1-62 =-9 + 6 =-3 Work Practice 11