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Direct Variaition Notes - 3.4

Lesson 3.4: Direct Variation

W.A.L.T.

write and graph direct variation equations

solve problems involving direct variation direct variation - described by an equation of the form y = kx or y/x = k

k is not equal to 0 (it can be positive or negative)

illustrates a constant rate of change

k is called the constant of proportionality, or the constant of variation

Example:

1) Suppose y varies directly as x, and y = 72 when x = 8

a) Write a direct variation equation that relates x and y. y = 9x

b) Use the direct variation equation to find x when y = 63 63 = x

x = 63/9

x = 7