1. Lesson 8-4: Direct, Joint, and Inverse Variation

2. Direct Variation y varies directly as x if there is a nonzero constant, k, such that y = kx *k is called the constant of variation 1. Plug in the two values you have and solve for the missing variable 2. Plug in that variable and the other given value to solve for the requested answer

3. Example If y varies directly as x and y = 12 when x = -3, find y when x = 16.

4. Joint Variation y varies jointly as x and z if there is a nonzero constant, k, such that y = kxz * Follow the same directions as before

5. Example Suppose y varies jointly as x and z. Find y when x = 8 and z = 3, if y = 16 when z = 2 and x = 5.

6. Inverse Variation y varies inversely as x if there is a nonzero constant, k, such that xy = k or y= kxkx

7. Example If y varies inversely as x and y = 18 when x = -3, find y when x = -11