QUESTION !
Which of the following charge distributions produces V(x) = 0 for all points on the x axis? ( we are defining V(x) º 0 at x = ¥ )
Therefore, to make V(x)=0 for all x, we must have the +Q and -Q contributions cancel, which means that any point on the x-axis must be equidistant from +2mC and -2mC and also from +1mC and -1mC.