The force f of attraction between two bodies varies jointly as the weights of the two bodies and inversely as the square of the distance d between them. express this fact as a variation using c as a constant. use m1 and m2 for the weights of the two bodies.

We have that F is proportional to m1. Hence, we have that F=m1*c when we change the first mass. We also have that F=m2*c when we only change the 2nd mass. Since F scales inversely with the square of the distance, we have that . Combining all of the facts above, we get that F=c* where c is a constant.