Particles of the charges q1=+5e (at origin) and q2=-15e are fixed in place with a separation of d=0.24m. With V=0 at infinity, what are the finite (a) positive and (b) negative values of x at which the net electric potential on the x axis is zero?
3. The problem I encounter
I can get the answer but I don't understand the position considered. Where do I consider my x value to be? Why don't we consider x to be greater than d? Why do we only consider for 0<x<d or x<d?