1. Multiplication of
Integer Numbers
I can multiply positive and
negative numbers.

2. Three Ways
There are three ways to write
multiplication.
 3 x 4 or 3(4) or
With variables
4y ab
3i4

3. Multiplication
 When you first learned multiplication, your book
had pictures of equal number of objects in
several rows.
 You learned that 3 × 4 meant “three fours.”
 3 × 4 = 4 + 4+ 4
 Thus a Pos x Pos = Pos #

4. Negative Numbers
 3 × (-4) means “three negative fours”
 3 × (-4) = (-4)+(-4)+(-4) = -12
 Using the addition rules you get -12
 Thus a Pos x Neg = Neg #

5. Multiplication Rules:
 a POSITIVE times a POSITIVE is POSITIVE
 a NEGATIVE times a NEGATIVE is POSITIVE
 a POSITIVE times a NEGATIVE is NEGATIVE
 a NEGATIVE times a POSITIVE is NEGATIVE

6. Another way to think about multiplication
The product of two integers with the same
sign is POSITIVE.
The product of two integers with different
signs is NEGATIVE.

7. You have $400 in a checking account.
Over the next several weeks, you make 6
withdrawals of $40 each.
How much have you withdrawn?
How much is left in the account?

8. You have $400 in a checking account.
Over the next several weeks, you make 6
withdrawals of $40 each.
How much have you withdrawn?
How much is left in the account?
$240
$160

9. GUIDED PRACTICE for Examples 1, 2 and 3
2. –1(4)
4. –6(–11)
5. –1(–12)(–9)
Find the product.
3. 7(0)

10. GUIDED PRACTICE for Examples 1, 2 and 3
2. –1(4)
4. –6(–11)
5. –1(–12)(–9)
= –108
Different signs, so product is negative.
Same sign, so product is positive.
Product of an integer and 0 is 0.
Multiply from left to right.
Multiply.
Find the product.
= –4
3. 7(0) = 0 property of zero
= 66
= 12(–9)

11. Order of Operations
A set of rules to simplify a numerical
expression.
1.Evaluate expressions inside grouping
symbols (brackets and parenthesis)
2.Multiply and divide from left to right
3.Add and subtract from left to right

12. GUIDED PRACTICE for Examples 1, 2 and 3
Evaluate the expression when a = 3, b = –4, and c = –8 .
1. ac – b = 3(–8) – (–4)
2. ac + b = 3(–8) + (–4)

13. GUIDED PRACTICE for Examples 1, 2 and 3
Evaluate the expression when a = 3, b = –4, and c = –8 .
1. ac – b Substitute 3 for a , –4 for b and –8 for c.= 3(–8) – (–4)
= (–24) – (–4)
= –20 Subtract.
Multiply.
2. ac + b Substitute 3 for a , –4 for b and –8 for c.= 3(–8) + (–4)
= (–24) + (–4) Multiply.
= –28 Add.

14. 9922
==
(-9)(-9)22
==
-9-922
==

15. 9922
== 9 x 9 =9 x 9 = 8181
(-9)(-9)22
== -9 x- 9 =-9 x- 9 = 8181
-9-922
== -81-81

16. If there are an even number of negative
signs, the answer is __________.
If there are an odd number of negative
signs, the answer is __________.
positive
negative

17. EXAMPLE 3 Evaluating an Expression with Integers
Evaluate a2
+ 3b when a = –5 and b = –11.
+ 3ba2

18. EXAMPLE 3 Evaluating an Expression with Integers
Evaluate a2
+ 3b when a = –5 and b = –11.
+ 3ba2 + 3(–11)= (–5)2
= 25 + 3(–11)
Substitute –5 for a and –11 for b.
Evaluate the power.
= 25 + (–33)
= –8
Multiply.
Add.

19. Assignment: