1. Multiplying & Dividing Integers Section 2-7 & 2-8

2. Something special about ‘0’ Zero property of multiplication –Anything times 0 = ‘zero’ –‘0’ divided by anything = ‘0’

3. Multiplication & Division Rules! Same Signs pos x posorpos ÷ pos neg x negor neg ÷ neg answer is Positive! Opposite Signs pos x neg orpos ÷ neg neg x pos or neg ÷ pos answer is Negative!

4. Why are opposites signs negative? Multiplication is addition repeated over and over again. For example, 4(– 2) is the same as: (– 2) + (– 2) + (– 2) + (– 2) =

5. Why do two negatives make a positive? The teacher says so! Don’t believe? Follow the pattern: ( 2 )(– 4) = ( 1 )(– 4) = ( 0 )(– 4) = (–1)(– 4) = (–2)(– 4) = +4

6. What about exponents and expressions? Exponents:  Write the equation as a product of the same factor. Then multiply.  Hint: what happens when the exponent is even? Odd? Variable expressions:  Substitute, and put each number in ( ).

7. Practice Example 1: – 16(– 5) = Example 2:12(– 11) = Example 3: 5(– 5)(– 5) = Example 4: 4(– 3)(– 2)(– 3) = 80 – 132 125 – 72

8. Practice Example 5: – 85 ÷ (– 5) = Example 6:28 ÷ (– 4) = Example 7: Example 8: 17 – 7 – 8 – 3

9. Evaluate the expression When f = – 1, g = 7, and h = – 10 Example 9: 4h Example 10: Example 11: gh + h – 40 70 – 80

10. Evaluate the expression When r = 12, s = – 4, and t = – 6 Example 12: 72 ÷ t Example 13: Example 14: rs ÷ 16 – 12 2 – 3

11. How to keep it simple Again, work with just 2 numbers at a time. Memorize your multiplication & division rules Know the difference between those and the “addition” rules Always ask, “positive or negative?”

12. Homework Worksheet – Integers – Review rules Next Test! –Friday, October 3, 2008! Need help? Practice, practice, practice –http://www.321know.com/grade7.htm#topic186http://www.321know.com/grade7.htm#topic186