1. Warm-up Solve. 1. 8x – 9 = 23 2. 9x + 12 = 4x + 37 3. 6x – 8 = 7x + 3
x = – , or –5 3

2. Homework Review

3. CCGPS Coordinate Algebra Day 13 (8-29-12)
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
Today’s Question:
How do I use order of operations to solve for a specified value?
Standard: MCC9-12.A.CED.4

4. Solving Equations and Formulas
Objectives:
Solve literal equations (formulas) for a specified variable
Apply these skills to solve practical problems

5. 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?

6. What it means to solve:
To solve for x would mean to get x by itself on one side of the equation, with no x’s 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 y’s on the other side. (y = __ )

7. 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?
y is being added to -5x.

8. 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 in one variable 
Ex: -5x + y = y -y -5x = y x = y = 56 + y -5 5

9. Let’s try another: Ex: Solve 2x - 4y = 7 for x. +4y + 4y 2x = 7 + 4y
x = 7 + 4y 2
This fraction cannot be simplified unless both terms in the numerator are divisible by 2.

10. Another example: Solve a(y + 1) = b for y. a a y + 1 = b a - 1 -1
y = b - 1 a

11. Try a few on your own. Solve P = 1.2W for W. H2
Solve P = 2l + 2w for l.
Solve F = 9C + 32 for C. 5

12. The answers: DO UNDO · 2 -2w +2w ÷ 2 l = P - 2w 2
DO UNDO · 1.2 · H2 ÷ H2 ÷ 1.2 W = PH2 1.2
DO UNDO
· w
+2w ÷ 2
l = P - 2w 2

13. The answers: DO UNDO x 9/5 - 32 + 32 ÷9/5 or times 5/9 C = 5 (F – 32)