Author: mark_cameron
Last saved by: MHE
Company: McGraw-Hill

Lesson 1-4

Example 1 Add Integers with the Same Sign
Find –6 + (–3).

Use a number line.
•	Start at zero. 	
•	Move 6 units left.
•	From there, move 3 units left.

So, –6 + (–3) = –9.

Example 2 Add Integers with Different Signs 
Find 7 + (–5).

Use a number line.
•	Start at zero.
•	Move 7 units right.
•	From there, move 5 units left.

So, 7 + (–5) = 2.

Example 3 Add Integers with Different Signs
Find –3 + 2.

Use a number line.
•	Start at zero.
•	Move 3 units left.
•	From there, move 2 units right.

So, –3 + 2 = –1.

Example 4    Add Integers with Different Signs
Find –16 + 7.

–16 + 7 = –9		To find –16 + 7, subtract  from . 
			The sum is negative because  > .

Example 5    Add Three or More Integers
Find –3 + (–10) + 5.

–3 + (–10) + 5	= [–3 + (–10)] + 5	Associative Property
		= –13 + 5		Simplify.
		= –8

Example 6    Use Integers to Solve a Problem
MONEY    The starting balance in a checking account is $100. What is the balance after checks for $15 and $65 are written?

Writing a check decreases the account balance, so the integers are –15 and –65. Add these integers to the starting balance to find the new balance.

100 + (–15) + (–65) = 100 + [(–15) + (–65)]	Associative Property
	= 100 + (–80)	–15 + (–65) = –80
	= 20	Simplify.

The balance is now $20.