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**Astronomy Que!!!!!**

**1. Homework Statement**

Three stars lie on a line (1,2,3). The distance from star 1 to star 3 is labelled as D. If star 1 is four times that of star 3, and seven times of star 2, what is the distance between star 1 and 2 if the net force of star 2 is zero?

**2. Homework Equations**

F=[tex]\frac{Gm1m2}{r^{2}}[/tex]

**3. The Attempt at a Solution**

Since the net force for star 2 is zero, I know that the force between star 1 and 2 is the same as the force between start 2 and 3

[tex]\frac{Gm1m2}{r^{2}}[/tex]=[tex]\frac{Gm2m3}{r^{2}}[/tex]

I tried to sub in values to find the force between star 1 and 3

F=[tex]\frac{Gm3(4m3)}{D}[/tex]

but i'm not sure where to go from here...

Thank you