Beginning Algebra, 11th Edition

Adding Two Negative Numbers

Find each sum.

(a)

(b) - 8 + 1 - 122 =- 20 (c) - 15 + 1 - 32 =- 18 NOW TRY

- 2 + 1 - 92 =- 1 |- 2 |+ |- 9 | 2 =- 12 + 92 =- 11

EXAMPLE 2

38 CHAPTER 1 The Real Number System

NOW TRY
EXERCISE 2
Find the sum.

• 6 + 1 - 112

NOW TRY ANSWERS

2. 
   
   
   
   • 17 3.- 4 4. - 9
   
   
   
   

–3 –2 –1 0 1 2 3 4 5

–2

5

 2  5  3

FIGURE 14 NOW TRY

Adding Numbers with Different Signs

To add two numbers with differentsigns, find the absolute values of the numbers

and subtract the lesser absolute value from the greater. Give the answer the same

sign as the number having the greater absolute value.

Example: - 12 + 6 =- 6

Adding Numbers with Different Signs

Find the sum

Find the absolute value of each number.

and

Then find the difference between these absolute values: The sum will

be negative, since

- 12 + 5 =- 7 NOW TRY

|- 12 | 7 | 5 |.

12 - 5 = 7.

|- 12 | = 12 | 5 |= 5

- 12 +5.

EXAMPLE 4

NOW TRY
EXERCISE 3
Use a number line to find the
sum.

4 + 1 - 82

NOW TRY
EXERCISE 4
Find the sum.

8 + 1 - 172

OBJECTIVE 2 Add two numbers with different signs.

Adding Numbers with Different Signs

Use a number line to find the sum

Step 1 Start at 0 and draw an arrow 2 units to the left. See FIGURE 14.

Step 2 From the left end of this arrow, draw a second arrow 5 units to the right.

The number below the end of the second arrow is 3, so - 2 + 5 =3.

- 2 + 5.

EXAMPLE 3

Adding Numbers with the Same Sign

To add two numbers with the samesign, add the absolute values of the numbers.

The sum has the same sign as the numbers being added.

Example: - 4 + 1 - 32 =- 7

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