Section 2.2 Addition of Integers 93 Skill Practice Use a number line to add. 5 4 3 2 1 0 1 2 3 4 5 3. 3 122 4. 3 122 Answers 3. 1 4. 5 b. 5 3 2 Move 3 units right. 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 Start here. Begin at 5. Then, because we are adding positive 3, move to the right 3 units. The sum is 2. Using a Number Line to Add Integers Example 2 Use a number line to add. a. 5 132 b. 5 132 Solution: a. 5 132 2 Move 3 units left. 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 Start here. Begin at 5. Then, because we are adding negative 3, move to the left 3 units. The sum is 2. b. 5 132 8 Move 3 units left. 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 Start here. Begin at 5. Then, because we are adding negative 3, move to the left 3 units. The sum is 8. 2. Addition of Integers It is inconvenient to draw a number line each time we want to add signed numbers. Therefore, we offer two rules for adding integers. The first rule is used when the addends have the same sign (that is, if the numbers are both positive or both negative). Adding Numbers with the Same Sign To add two numbers with the same sign, add their absolute values and apply the common sign. TIP: In Example 2, parentheses are inserted for clarity. The parentheses separate the number 3 from the symbol for addition, . 5 132 and 5 132
miller_prealgebra_2e_ch1_3
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