# 3-3 Solving Multi-Step Equations Warm-up Solve. x=4 x = 5 2. 9x + 12 = 4x + 37 3. 6x 8 = 7x + 3 x = 11 1 1 3 23, or 5 x =

4. 2 x + 3 8= 4 4 1. 8x 9 = 23 More practice Solve. 5. 25 = -5x -10 x=7 x = -16

6. -4x 8 = -2x + 24 7. 6x 14 = -2(x + 3) x = 1 Homework Review GSE Algebra I UNIT QUESTION: Why is it important to understand the relationship between quantities? Standard: MCC9-12.N.Q.1-3, MCC9-12.A.SSE.1, MCC9-12.A.CED.1-4 Todays Question: How do I use order of operations to

solve for a specified value? Standard: MCC9-12.A.CED.4 Solving Equations and Formulas Objectives: Solve literal equations (formulas) for a specified variable Apply these skills to solve practical problems Definitions: An equation is a mathematical sentence that contains an equal sign ( = ). Ex: y = 3x A formula is an equation that states a rule for

the relationship between certain quantities. Ex: A = lw What do A, l, and w stand for? What it means to solve: To solve for x would mean to get x by itself on one side of the equation, with no xs on the other side. (x = __ ) Similarly, to solve for y would mean to get y by itself on one side of the equation, with no ys on the other side. (y = __ ) The DO-UNDO chart 1) Solve the equation -5x + y = -56 for x. Ask yourself:

What is the first thing being done to x, the variable being solved for? x is being multiplied by -5. What is being done next? (-5) y is being added to -5x. DO UNDO -5 -y

+y Show all of your work! First, subtract y from both sides of the equation. Next, divide by -5. This process actually requires LESS WORK than solving equations Ex: -5x + y = -56 - y -y -5x = -56 - y

-5 -5 x = -56 - y = 56 + y -5 5 Lets try another: Complete the do-undo chart. + 4y xDO 2 UNDO

- 4y Ex: Solve 2x - 4y = 7 for x. +4y + 4y 2x = 7 + 4y 2 2 2 x = 7 + 4y 2 This fraction cannot be simplified

unless both terms in the numerator are divisible by 2. Another example: Complete the do-undo chart. DO UNDO +1 x a a -1 Solve a(y + 1) = b for a

a y. y+1=b a -1 -1 y=b-1 a Try a few on your own. Solve P = 1.2W for W. 2

H Solve P = 2l + 2w for l. Solve F = 9C + 32 for C. 5 The answers: DO UNDO 1.2 H H 1.2 DO UNDO

2 -2w +2w 2 W = PH 1.2 l = P - 2w 2 2 2

2 The answers: DO UNDO x 9/5 - 32 + 32 9/5 or times 5/9 C = 5 (F 32) 9