1. Lesson 6-9: Variation Objective: Students will:
Find the constant of variation and setup direct and inverse variation equations
Use variation equations to solve problems

2. Direct Variation
Equations: or
Why direct?
Take or , where k = 2
If y goes up, x must go up
y and x move the same → direct
“k” is the constant of variation – must stay constant

3. Inverse Variation
Equations: or
Inverse → opposite → if y goes up, x must go down…
Choosing
Identify the variables
Ask: if the one value increases, what will the other do?
increase also → direct
decrease → inverse

4. Example 1
The force applied to a spring causes the length to increase. 8 pounds makes the spring 4 inches. Find k and write a general equation.
Example 2
A theater makes $900 with 200 people. Find k, write a general equation, and how much would it make with 500 people.