Solving Addition and Subtraction

Equations

Objective:

To solve addition and subtraction equations using required form and inverse operations.

NOTES:Addition and subtraction are

called inverse operations (opposites). They can be used to “undo” or “cancel” each other and help us to solve an equation for a missing value.

NOTES:However, the inverse operation must

be done on both sides of an equation so that it cancels an operation on one side and takes it to the other side. We will use required form and a check-step to prove each value is correct.

Notes:

Our goal is to isolate the variable.

To do this, we must remember, “What we do to one side, we have to do to the other.”

Solve. 22 = y – 11

22 = y – 11+ 11 + 11

33 = y + 0

33 = y

Check22 = y – 11?

22 = 33 – 11

22 = 22

Solve.A. 15 + n = 29

15 + n = 29–15 –15 0 + n = 14

n = 14

Check15 + n = 29

?10 + 14 = 29

29 = 29

Examples: Solve using required form and a check-step. Any “scratch” work should go on scratch paper.

Ex 1) 7 10x

Ex 2) 4 16y

Ex 3) 20 4z

Ex 4) 11 2.9y

Ex ) 15.37 76f

Ex 8) 25 13.4h

Homework:

1. -6(3x – 8) 2. (-m + 9)(-3) 3. (3)(-6 – x) 4. 2(x – y + 1) 5. 4(6p + 2q – 2p) 6. p(m+ 2)