Lesson 1-6

Example 1 Multiply Integers with Different Signs
Find 5(–6).

5(–6) = –30		The factors have different signs. The product is negative.

Example 2 Multiply Integers with Different Signs  
Find –7(3).

–7(3) = –21		The factors have different signs. The product is negative.

Example 3 Multiply Integers with the Same Sign
Find –3(–5).

–3(–5) = 15		The factors have the same sign. The product is positive.

Example 4 Multiply More than Two Integers
Find –4(3)(–2).

Method 1	Use the Associative Property
–5(3)(–2) = [–5(3)](–2)	Associative Property
	= –15(–2)		–5(3) = –15
	= 30			–15(–2) = 30

Method 2	Use the Commutative Property
–5(3)(–2) = –5(–2)(3)		Commutative Property
	= 10(3)		–5(–2) = 10
	= 30			10(3) = 30

Example 5 Divide Integers
Find –22  2.

–22  2 = –11		The dividend and the divisor have different signs. 
The quotient is negative.

Example 6 Divide Integers
Find –56  (–8).

 –56  (–8) = 7	The dividend and the divisor have the same sign. 
The quotient is positive.

Example 7 Evaluate Algebraic Expressions
Evaluate –3x – y if x = –2 and y = –4.

–3x – y = –3(–2) – (–4)	Replace x with –2 and y with –4.
 	= 6 – (–4)		The product of –3 and –2 is positive.
 	= 6 + 4		To subtract –4, add 4.
 	= 10			Add.

Example 8 Find the Mean of a Set of Integers
WEATHER  In Smalltown, the low temperatures for one week in January were 10F, 15F, –5F, 25F, –15F, –10F, and 29F. Find the mean low temperature for the week.

To find the mean of a set of numbers, find the sum of the numbers. The divide the result by how many numbers there are in the set.

Find the sum of the numbers. 
Divide by the number in the set.	
	= 7			Simplify.

The average low temperature for the week was 7F.