Homework Help: What is the distance of the third charge?

1. The problem statement, all variables and given/known data

Three point charges, 3.0 [tex]\mu[/tex]c, -5.0[tex]\mu[/tex]c and 0 [tex]\mu[/tex]c.

If the distance from point 1 (3.0) and point 2 (-5.0) is 40m, what is the distance from point 2 to point 3?

2. Relevant equations

coulombs law


[b

3. The attempt at a solution

I don't know how to start this :(

 

I'm not really sure since I only remembered this problem by memory :( but if the third body WAS neutral and they ARE in equilibrium, how would you answer this? :D

 

um, if that's so, is it then possible to be solved?

I need to use this formula :D ?

Fe = [tex]\frac{ Kq1q2 }{ r2 }[/tex]