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Section 1.8 Solving Addition and Subtraction Equations

Section 1.8 solving add sub equations (math)

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Page 1: Section 1.8 solving add sub equations (math)

Section 1.8Solving

Addition and Subtraction Equations

Page 2: Section 1.8 solving add sub equations (math)

Which word do you think “Equation” has a connection

to?

Page 3: Section 1.8 solving add sub equations (math)

YOU’RE CORRECT!

Page 4: Section 1.8 solving add sub equations (math)

An equation is a

mathematical sentence

that contains an equal sign.

Page 5: Section 1.8 solving add sub equations (math)

The part on the left side of the equal sign has the same value as the part on the right side. One or

both sides may contain a variable.

Page 6: Section 1.8 solving add sub equations (math)

What is a variable?

A. A number that changes constantly.

B. A letter or symbol that stands for a number.

C. A number that varies as you move away from zero.

Page 7: Section 1.8 solving add sub equations (math)

YOU’RE CORRECT!

Page 8: Section 1.8 solving add sub equations (math)

A variable is a letter or

symbol that stands for a

number.

Page 9: Section 1.8 solving add sub equations (math)

To solve an equation, you

must find what the variable

represents so that the two

parts are equal.

Page 10: Section 1.8 solving add sub equations (math)
Page 11: Section 1.8 solving add sub equations (math)

Equations are like balance scales. In order to keep a scale balanced you must have the same amount of weight on both sides.

Page 12: Section 1.8 solving add sub equations (math)

If I took one block away from the left side, what would I have to do to keep

the scale from tipping?

Page 13: Section 1.8 solving add sub equations (math)

If I added 6 more apples to the right side, how could I keep the scale from

tipping?

Page 14: Section 1.8 solving add sub equations (math)

To keep an equation equal,

we must do exactly the same thing to each side

of the equation. If we add a number to one side, we

must add that same number to the other side

and vice versa.

Page 15: Section 1.8 solving add sub equations (math)

Addition and subtraction are called “opposite

operations” because they can ‘undo’

each other.

Page 16: Section 1.8 solving add sub equations (math)

What are the other two opposite

operations?

Page 17: Section 1.8 solving add sub equations (math)

Multiplication and division are opposite operations,

too!

Page 18: Section 1.8 solving add sub equations (math)

for Solving Addition and Subtraction Equations

Page 19: Section 1.8 solving add sub equations (math)

1. Look to see what side the

variable is on.

Page 20: Section 1.8 solving add sub equations (math)

2. Decide what

operation is being shown.

Page 21: Section 1.8 solving add sub equations (math)

3. Do the opposite of

that operation to both sides.

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4. Write what

number the variable

stands for (ex: a = 2).

Page 23: Section 1.8 solving add sub equations (math)

5. Check the solution by “plugging” the number back into the equation to see if the sides are equal.

Page 24: Section 1.8 solving add sub equations (math)

Example 1m + 18 = 34 Look for variable

-18 -18 Do the opposite

m = 16 Write what m is

m + 18 = 34

16 + 18 = 34 Plug in m

34 = 34 Solution is correct!

Page 25: Section 1.8 solving add sub equations (math)

If you check your solution and you do

not come out with the same numbers, then your solution is not correct. Therefore,

you must rework the problem.

Page 26: Section 1.8 solving add sub equations (math)

Always check your answers to equations.

It is the only way to make sure you get a

problem correct. Why miss a problem when

you can get all of them correct?

Page 27: Section 1.8 solving add sub equations (math)

Example 2 68 = y + 43 Look for variable

-43 -43 Do the opposite

25 = y Write what y is

68 = y + 43

68 = 25 + 43 Plug in y

68 = 68 Solution is correct!

Page 28: Section 1.8 solving add sub equations (math)

Example 3 t - 14 = 22 Look for variable

+ 14 +14 Do the opposite

t = 36 Write what t is

t - 14 = 22

36 - 14 = 22 Plug in t

22 = 22 Solution is correct!

Page 29: Section 1.8 solving add sub equations (math)

Try These...1. r + 5 = 18

2. m - 26 = 59

3. 102 = x - 15

4. a + 39 = 56

r = 13

m = 85

117 = x

a = 17

Page 30: Section 1.8 solving add sub equations (math)

Let’s do Checking for

Understanding Page 47 # 4 - 9

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Prediction:You will show all of the

steps (including checking) as you have been shown today or

credit will not be given for your homework.

Page 32: Section 1.8 solving add sub equations (math)

Are there any questions

about solving addition or subtraction equations?

Page 33: Section 1.8 solving add sub equations (math)

Homework:

Page 48 12-34 even

Don’t forget to check your solution!