1. The problem statement, all variables and given/known data Two point charges q and λq located at the points, x=a & x=μa respectively. If the sum of the two charges is constant,what is the value of λ for which the magnitude of the electrostatic force is maximum? 2. Relevant equations 3. The attempt at a solution For force to be maximum dF/dq =0 and d^F/dq^2 <0. When I tried to calculate dF/dq =0 I got λ=0.