Download Lesson

Name ____________________________
Chapter 1 Lesson 4
Math 8 Topic: Multiplying & Dividing Integers What you have to leave
here knowing:
1) How to multiply
integers.
DO IT:
1) Evaluate each of the following:
a) 7 – 3 + 2
2) How to divide
integers.
b) 5 x 4 + 33
2) If x = 12, b = 4 and c = 2, evaluate:
!!!!
!!
Find each sum. Model with algebra tiles.
3) -5 + 2
4) -3 + (-7)
SELECT HOMEWORK ANTZAS:
1) 0
2) 17
3) 0
4) -15
12) -9
7) -14
8) 14
13) -14
14) 5x
TODAY’S LESSON
Continued on next page.
9) 3
5) -2 + -1
5) -4
6) 3
10) -2
11) 9
Arriving at the rules for multiplying and dividing ……………. sequences:
3 x 3 = ____
3 x 2 = ____
What do you notice happens when you multiply by a
negative?
3 x 1 = ____
3 x 0 = ____
3 x -1 = ____
3 x -2 = ____
Two More Sequences and the Rule for Multiplying & Dividing:
4 x 2 = ____
-5 x 2 = ____
4 x 1 = ____
-5 x 1 = ____
4 x 0 = ____
-5 x 0 = ____
4 x -1 = ____
-5 x -1 = ____
4 x – 2 = ____
-5 x – 1 = ____
Method #2………… Reasoning Well Together.
What does it mean to negate? ___________________________________________.
When you multiply by a negative number, you are multiplying by both the negative and
the number. When you get to multiplying by a negative, change the sign.
Example: 3 x 3 = 9, but 3 x -3 = -9 because you multiplied BY a negative.
5 x 2 = 10, but 5 x -2 = -10 because you multiplied BY a negative.
-4 x 5 = -20, but -4 x -5 = +20 because you multiplied BY a negative.
When multiplying or dividing, the sign is what you start with unless you multiply BY a
negative. If so, change the sign.
Skill & Drill:
1) 4 x 3 = ____
2) 4 x -3 = ____
3) -4 x 3 = ____
4) -4 x -3 = ____
5) 10 ÷ 5 = ____
6) -10 ÷ 5 = _____
7) -10 ÷ -5 = ____
8) 10 ÷ -5 = ____
PRACTICE
Perform the following operation and express in simplest form.
1) -3x + -8x
2) -3 x -8
3) 5 x (-4)
4) -2 – (-7)
5) John says the sum of two negatives is always a negative. Is he right? Why or why
not?
6) Jen says the product of two negatives is always a positive? Is she correct? Why or
why not?
One last thought ……. What do you think -5x + 2x equals? What about (-3x2) - (-2x2)?
Available Internet Resources:
Khanacademy.com scroll down the page until you come to sections on Prealgebra.
My website:
http://pages.pmschools.org/sites/rlindquist/Mr._Lindquists_Math_Land/Daily_Math_Blo
g/Daily_Math_Blog.html
HOMEWORK:
Let’s take a moment to review what we have learned so far this unit.
1) The order of operations is ……
_________________________
_________________________
_________________________
_________________________
2) What does evaluate mean? _______________________________________
3) How do you evaluate 105? _________________________________________
4) How do you add if the signs are the same? ____________________________
5) How do you add if the signs are different? _____________________________
6) Is there really such a thing as subtraction? _____________________________
7) What is your favorite way to remember how to multiply or divide signed numbers?
Why do you like this way better?
_____________________________________________________________________
Evaluate each expression for a = 2, b = 8 and c = 3.
1) b ÷ a – −𝑐
2) c – a + b
Find each sum or difference:
3) -2 - -9
4) -5 + (-7)
5) 3 + -1
6) -8 -5
7) -3 – (-11)
8) -23 - -11
9) If a = 7 and b = -4, find ab.
10) Find the sum of -9 and 2.
11) From 7 subtract -2.
12) Subtract 7 from -4.
13) If x = -4 and y = -12, find y÷x.
14) Find the sum of -9x and -2x.
15) Subtract 7y from 2y.
1) 3 + -8 = ____ 2) -4 + -4 = ____3) -7 + 5 = ____ 4) 4 – (-5) = ____5) -3 – 4 = ____
Evaluate each expression if x = 4, y = -2 and z = -3.
6) y – 2 + x
7) 35 – z + x
9) -4 – 5 + 1 - 4
8) y − z
10) 5 – 4 + 2 – (-8)
11) -9 – (-6 – 2)
Always, sometimes, never and explain your antza:
12) The sum of two negatives is always negative.
_____________________________________________________________________
13) The product of two negatives is always negative.
_____________________________________________________________________
14) A negative minus a negative is always a negative.
_____________________________________________________________________
Find each product or quotient.
15) -3 ⋅ 6
16) -7 ⋅ 10
17) -4(-2)
18) 6(-7)
19) 8(-11)
20) -2(-8)
21) 9 ⋅ 5
22) -12 ⋅ 4
23) -20 ÷ (-5)
24) -20 ÷ 5