Find the potential everywhere on all axes.?

Question

A point charge q1 is at the origin and second point charge q2 is at infinity. Use a three dimensional system to answer this problem. (x,y and z).

Answer 1

The point charge q2 at infinity may be viewed as a point charge -q2 at the origin. Hence the potential is:
(q1-q2)/(4*pi*e*r)
= (q1-q2)/(4*pi*e*sqrt(x^2+y^2+z^2))