1. Lesson 12.1 Inverse Variation pg. 642
Objectives: To graph inverse variation.
To solve problems involving inverse variation.

2. Inverse Variation
y varies inversely as x if there is some nonzero constant k such that xy = k

3. Inverse Variation Problems
To solve some inverse variation problems, there are two steps:
(1) First find the value of k
(2) Use the value of k to find a specific value of x or y

4. Graphing Inverse Variation
To graph inverse variation choose values for x and y whose product is k

5. Ex. 1: Graphing inverse variation
Graph an inverse variation in which y varies inversely as x, and y=1 when x=4

6. Graph an inverse variation in which y varies inversely as x, and y=-6 when x=-210
-10

7. Product Rule for inverse variation
The product rule x1 y1 = x2y2 can be used to solve inverse variation problems.

8. 1. If y varies inversely as x and y = 5 when x =12, find x when y = 15
Ex. 2: Write and inverse variation equation that relates x and y. Assume that y varies inversely as x. Then solve.
1. If y varies inversely as x and y = 5 when x =12, find x when y = 15

9. 2. If y varies inversely as x and y = 8 when x =6, find y when x = 4