Physics
posted by Fernando .
A spaceship of mass m is located between two planets of masses M1 and M2; the distance between the two planets is L. Assume that L is much larger that the radius of either planet. What is the position of the spacecraft (given as a function of L, M1, and M2) if the net force on the spacecraft is zero?

GM1/r^2=GM2/(Lr)^2 solve for r, which is the distance from the center of M1

I tried that... I get L/(L+sqrt(M2M1)) but that's not it...

recheck your algebra, dimensional analysis shows it is impossible.