1. The problem statement, all variables and given/known data Say there is a charge of +3 at the origin and a charge of -7 at .5m Where would a third charge of arbitrary sign have to be for equilibrium to be reached? 2. Relevant equations 3. The attempt at a solution so I've widdled this down to 3 / r^2 = -7/(.5+r)^2 but am having problems solving for r. Algebra is tough!!! anyone want to give me tips here? In the equation I have I already divided out the third charge and the k term.