A direct variation function contains the points (-9, -3) and (-12, -4). Which equation represents the function?
A$y=-3 x$
B$y=-\frac{x}{3}$
C$y=\frac{x}{3}$
D$y=3 x$
A$y=-3 x$
B$y=-\frac{x}{3}$
C$y=\frac{x}{3}$
D$y=3 x$