Write an equation of the direct variation that includes the point (9, –12).

Question

anonymous · Answer

The direct variation equation has the form y=kx, where k is the constant of variation.  We can find the value of k by substituting the values for x and y  using any given point such as (9, -12) and solving for k.$$-12=k*9$$or$$k=\frac{-12}{9}=\frac{-4*\cancel3}{3*\cancel3}=\frac{-4}{3}$$Now we can write y=kx with the found constant of variation:$$y=-\frac{4}{3}x$$
This is an equation of the direct variation that includes the point (9, –12).