Let G(x) = 1/(1 – x)2 =
(A) i
(B) i+1
(C) 2i
(D) 2i
Answer: (B)
Explanation: B is the correct option. Let us put values
S = 1 + 2x + 3x2 + 4x3 + .......... Sx = x + 2x2 + 3x3 + .......... S - Sx = 1 + x + x2 + x3 + .... S - Sx = 1/(1 - x) [sum of infinite GP series with ratio < 1 is a/(1-r)] S = 1/(1 - x)2