2. Multiplying integers
If the signs are the same, the sign of the
answer is positive.
If the signs are different, the sign of the
answer is negative.
negative x negative = positive
negative x positive = negative
positive x positive = positive
3. Properties
• Commutative property • Identity property
– order changes – product of a number and
– product stays the same one is the number
– 5(4) = 4(5) – 5(1) = 5
• Associative property • Property of zero
– grouping changes – product of a number and
– product and order stay the zero is zero
same – 6(0) = 0
– (6 * 2) * 3 = 6 *(2 * 3) • Property of negative one
– Product of a number and
negative one is the
opposite of the number
– 77 (-1) = - 77
4. Example 1 Multiply real numbers
Find the product.
a. 2 (–5 ) ( – 4) = ( –10) (–4 ) Multiply 2 and – 5.
= 40 Same signs; product is positive.
1 1
b. – (– 4) (–3) = 2 (–3) Multiply – and – 4.
2 2
= –6 Different signs; product is negative.
5. Guided Practice for Example 2
2. Which property is used in the equation
5• ( – 6 ) = – 6 • 5?
ANSWER commutative property of multiplication
6. Example 3 Use properties of multiplication
Find the product ( –4x) • 0.25. Justify your steps.
( –4x ) • 0.25 = 0.25 • ( –4x )
= [0.25 • ( –4 )] x
= –1 • x
= –x
7. Guided Practice for Examples 3 and 4
Find the product. Justify your steps.
3
( 5y)
10
