Hi. I would appreciate some help with this point charge problem. I think I understand the general set up, but don't know where to go from there. 1. The problem statement, all variables and given/known data Two point charges are placed on the x axis as follows: Charge q1 = +4.00nC is at x=0.400m, and charge q2 = +2.00nC is at x=-0.200m. State, in x and y coordinates, where a negative point charge, q3 = -4.73nC, must be placed to have a zero net force exerted on it by q1 and q2. 2. Relevant equations I know that F = (k*q*Q)/r2 and that the force from q1 acting on q3 (F13) has to be equal to the force from q2 acting on q3 (F23) for the net force to = 0. 3. The attempt at a solution Where I am getting lost is in relation to the distances between the charges. If I don't know the distance between q1 and q3, and q2 and q3, how can I do the problem? And I can't rely on the Pythagorean theorem because there is no guarantee that a right angle is formed. I know my best chance at solving this is a quadratic equation, but I don't know how to get to that point. It has been a LONG time since I took algebra, so I may be overlooking something very simple. This is what I have: F13 = (k*q1*q3)/r132 = F23 = (k*q2*q3)/r232 things cancel and it simplifies to q1/r132 = q2/r232 From here I have absolutely no idea where to go. Thanks for your help.