Two point charges of magnitude +40x10^-6C and -60x10^-6C are placed 50 cm apart. What is the distance from +40x10^-6C charge along the line joining the two point charges if the resultant potential is zero

Answer 1

potentials are scalar, so you can addthem

V=0=40E6/x-60E6/(.5-x)

solve for x

Answer 2

What is the exact formula to solve the question above?