The document discusses direct variation, which is when a dependent variable y varies proportionally to an independent variable x. It provides examples of direct variations and equations of the form y = kx, where k is the constant of variation. It shows how to identify direct variations from examples, write direct variation equations, and graph direct variations.

1. Objective- To use and write equations involving direct variation Direct Variation- When a dependent variable y is proportional to and varies directly with an independent variable x. y = k x k = constant of variation (any non-zero real number) Circle the examples of direct variation.

2. 3 3 The variable y varies directly with x. When x = 3, y = 21. Find the value of y when x = 8. y = k x y = 7 x

3. It takes 5 cups of flour to bake 65 cookies. How many cookies can be made with 7 cups of flour? Let x = cups of flour Let y = # of cookies 5 5 y = k x y = 13 x

4. Graph a Direct Variation x y -3 -2 -1 0 1 2 3 4 -1.5 -1 -0.5 0 0.5 1 1.5 2 x y

5. x x Use Data to Write a Direct Variation Pinky Forefinger (x) (y) 5.4 6.8 7.5 8.1 cm 6.5 8 9 9.8 cm Write a direct variation equation that relates the length of a person’s forefinger to their pinky. Let y = forefinger length Let x = pinky length