I think that this problem should be easy but for some reason I don't think I really understand it. A charge of +2q is placed at the origin and a second charge of -q is placed a x = 3cm. Where can a third charge +Q be placed so that it experiences a zero force? I figure that F3 = F1 + F2 = k2q/x^2 - kq/(x+0.03)^2 = 0 Cancelling out and cross multiplying gives 2(x+0.03) = x^2 Therefore the eq'n is x^2 + 0.12x + 0.0018 = 0 Using the quadratic eq'n to solve I found that x = -1.8 cm or x = -10.3 cm. Here's where I'm not sure, if they are both negative does that mean that they are to the left of the origin, and if so which is the correct one then??