Io is the largest of Jupier's moons with a mass 1/4000 of the mass of Jupiter.

The distance between the two bodies is 4.22x10^8m. Find the distance from Jupiter at which the resultant gravitational field is from the two bodies is zero.

Do i use Fc=Fg?

and find out the mass of Jupiter and the moon.

then use F=-Gm1m2/r^2 to work out the force on Jupiter,put the force back into mrw^2 with Io's mass and work out the radius? or am i completely work?

thanks.