Since the electrostatic potential v(r) is a solution of the Euler-
Cauchy equation rv00 + 2v
0 = 0, by multiplying r on both sides, we have a = 2
and b = 0. By (∗) and (∗∗), Y = 1 and Y = 1/s. Hence, we have y = −1/r
and y = 1. This gives the general solution
y = c1 + c2/r.