Suppose 'y' varies directly as 'x', and y=8 when x=-2. Which of the following is the correct equation to set up to solve for the constant of variation?
A) 8=k(-2)
B) -2=k(8)
C) -2/8=k/1
D) k=(-2)-8

Question

Suppose 'y' varies directly as 'x', and y=8 when x=-2. Which of the following is the correct equation to set up to solve for the constant of variation?
A) 8=k(-2)
B) -2=k(8)
C) -2/8=k/1
D) k=(-2)-8

welshfella · Answer

y = kx
plug in y=8 and x = -2

mathmale · Answer

Welshie is right.  y = kx is the standard equation for "direct variation."  Your job is to find the value of k that fits the given x and y.  Once you have completed this equation, you can apply it to the given new situation.