1. The problem statement, all variables and given/known data A -3.0 nC charge is on the x-axis at x = -9cm and a +4.0 nC charge is on the x-axis at x = 16 cm. At what point or points on the y-axis is the electric potential zero? 2. Relevant equations V = kq/r 3. The attempt at a solution I know the answer is +/- 12 cm but I have no clue as to how that number was achieved. Can anybody please help me out with this one?