Question

Find the direct variation equation of the graph through the points (0, 0) and (1, -2). Write in y=kx form.
A.y = 2x
B.y = -2x
C.y = 1/2 x
D.y = -1/2 x

Find the direct variation equation which passes through (0, 0) and (4, 1).
A.y = 4x
B.y = -4x
C.y = 1/4 x
D.y = -1/4 x

Answer 1

y = kx

-2 = k(1)

-2 = k

k = -2


So the equation is y = -2x

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y = kx

1 = k(4)

1/4 = k

k = 1/4


So the equation is y = 1/4 x

Answer 2

find the gradient m = rise/run. rise is -2, run is 1..... therefore m = -2

y-intercept is 0.... therefore the equation is y = -2x