if "y" varies directly with "x", find the constant of variation for an equation containing the following points (-1.5,4.5) and (2.8,-8.4)

$$\\y=kx\qquad $Where k is the constant of variation$\\\\ 4.5=k*-1.5\\\\ 4.5/-1.5=k\\\\ k=-3\\\\ check\\\\ -3*2.8=-8.4\quad $Yes that is what it needed to be$$ $