Page 149 - Basic College Mathematics with Early Integers

126 C HAPTE R 2 I INTEGERS AND INTRODUCTION TO VARIABLES

Adding Two Numbers with the Same Sign

Step 1 Add their absolute values.
Step 2 Use their common sign as the sign of the sum.

PRACTICE 4 Example 4 Add: -2 + 1-212
Add: 1-32 + 1-92
Solution:
Step 1 ƒ -2 ƒ = 2, ƒ -21 ƒ = 21, and 2 + 21 = 23.
Step 2 Their common sign is negative, so the sum is negative:
-2 + 1-212 =-23
Work Practice 4

PRACTICE 5–6 Examples Add.
Add.
5. -5 + 1-102 =-15
5. -12 + 1-32
6. 2 + 6 = 8
6. 9 + 5
Work Practice 5–6

When adding two numbers with different signs, as in Examples 1 and 3, the sign
of the result may be positive, negative, or the result may be 0.

Adding Two Numbers with Different Signs

Step 1 Find the larger absolute value minus the smaller absolute value.
Step 2 Use the sign of the number with the larger absolute value as the sign
of the sum.

PRACTICE 7 Example 7 Add: -14 + 35
Add: -3 + 59
Solution:
Step 1: ƒ -14 ƒ = 14, ƒ 35 ƒ = 35, and 35 - 14 = 21.
Step 2: 35 has the larger absolute value and its sign is an understood +:
-14 + 35 =+ 21 or 21
Work Practice 7

PRACTICE 8 Example 8 Add: 13 + 1-172
Add: 22 + 1-282
Solution:

Step 1: ƒ 13 ƒ = 13, ƒ -17 ƒ = 17, and 17 - 13 = 4.
Step 2: -17 has the larger absolute value and its sign is -:
PRACTICE 9–11 13 + 1-172 =-4
Add.
Work Practice 8
9. -46 + 20
10. 8 + 1-62 Examples Add.
11. -2 + 0 Copyright 2012 Pearson Education, Inc.
9. -18 + 10 =-8
10. 12 + 1-82 = 4
Answers
11. 0 + 1-52 =-5 The sum of 0 and any number is the number.
4. -12 5. -15 6. 14 7. 56
8. -6 9. -26 10. 2 11. -2 Work Practice 9–11