DIRECT VARIATION GOAL: WRITE AND GRAPH DIRECT VARIATION EQUATIONS Section 2-6:
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Transcript of DIRECT VARIATION GOAL: WRITE AND GRAPH DIRECT VARIATION EQUATIONS Section 2-6:
DIRECT VARIATION
GOAL: WRITE AND GRAPH DIRECT
VARIATION EQUATIONS
Section 2-6:
Direct Variation
Two variables x and y show direct variation, or vary directly, if y = kx where k is a nonzero constant called the constant of variation.
The graph of y = kx is a line with slope k. The y-intercept is 0 (zero), so the graph of any direct variation equation passes through the origin.
Example 1: Graph y = 2x
Graph y = 2/3 x
Graph y = -4x
Example 2:
A recipe for fruit punch uses 2 lemons to make 7 cups of punch. Write an equation relating the number of servings y to the number of lemons x. How many cups of punch can you make if you have 8 lemons?
Checkpoint:
The variables x and y vary directly. Write an equation that relates x and y. x= 3, y = -9
y = kx-9 = k*3k =-3y=-3x
Checkpoint:
The variables x and y vary directly. Write an equation that relates x and y. x = 10, y = 2
y = kx2 = k*101/5 = ky = 1/5 x
P. 103-10510-34 EVEN50-66 EVEN
HOMEWORK: