Chapter 20, Problem 108PP

Referring to Example 20-9 Suppose we can change the location of the charge −2q on the x axis. The charge +q (where q = 4.11 × 10^-9 C) is still at the origin. (a) Where should the charge −2q be placed to ensure that the electric potential vanishes at x = 0.500 m? (b) With the location of −2q found in part (a), where does the electric potential pass through zero in the region x < 0?