Given: 2x 5y 4

1
Given 2x 5y 4

• Find y when x -3, -1, 2, 6.
• Which method is more efficient?
• Substitute in values for x then solve for y.
• Solve for y, then substitute in values for x.

2
Rewriting Equations and Formulas

• Goals
• 1- Rewrite equations with more than one variable.
• 2- Rewrite common formulas

3
Rewriting an Equation with More than One Variable

• Solve 7x 3y 8 for y

4
Calculating the Value of a Variable

• Given x xy 1, find the value of y when x-1
  and x3.

5
Writing an Equation with More than One Variable

• You are organizing a benefit concert. You plan on
  having only two types of tickets adult and
  child. Write an equation with more than one
  variable that represents revenue from the
  concert. How many variables are in your equation?

Total Revenue
Adult Ticket Price
Number Of Adults
Number of Children
Child Ticket Price
x

x

6
Writing an Equation with More than One Variable

• Total Revenue R
• Adult Ticket Price P1
• Number of Adults A
• Child Ticket Price P2
• Number of Children C
• R P1(A) P2(C)

7
Using an Equation with More than One Variable

• For the concert your goal is to sell 25,000 in
  tickets. You plan to charge 25.25 per adult and
  expect to sell 800 adult tickets. You need to
  determine what to charge for child tickets. What
  should you charge if you expect to sell 200 child
  tickets? 300? 400?

8
Rewriting a Common Formula

• The formula for perimeter of a rectangle is P
  2L 2W. Solve for W.

9
Homework

• Pg. 29-30
• 24-30 even, 35-40

10
Applying a Common Formula

• You have 40 feet of fencing with which to enclose
  a rectangular garden. Express the gardens area
  in terms of its length only.