71. The charges are equidistant from the point where we are evaluating the potential – which is computed
using Eq. 25-27 (or its integral equivalent). Eq. 25-27 implicitlyassumes V
→ 0 as r → ∞. Thus, we
have
V =
1
4πε
0
+Q
R
+
1
4πε
0
−2Q
R
+
1
4πε
0
+3Q
R
which simplifies to Q/2πε
0
R.