1. The problem statement, all variables and given/known data A charge of +2q (a) is placed at the origin and a second charge of -q (b) is placed at x = 3.0 cm. Where can a third charge +Q (c) be placed so that it experiences a zero net force? 2. Relevant equations F = k(Q1)(Q2)/r^2 E = kQ/r^2 Quadratic? 3. The attempt at a solution After many attempts from varying angles I think I have it down to Fac + Fbc = 0 So: Fc = k(2q)(q)/(0.003 + x)^2 + k(-q)(q)/x^2 = 0 I can get this down to (k)(2q) + (k)(-q) = 0.003x + x^2, I assume to solve this problem I will need to use the quadratic equation (PLEASE if there is an easier way enlighten me) but for the life of me cannot figure out how to get these figures into the Ax^2 + bx + c format because there are two unknown variables (q and x). I assume because the qs are just factors of each other I probably do not need to actually know the value of q to solve for x. I am so lost... Am I even on the right path?