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Assam Mathematics Olympiad 2023 Category III Q13

Source:

September 11, 2024

Problem Statement

Let S(r)S(r) denote the sum of the infinite geometric series 17+17r+17r2+17r3+...17 + 17r + 17r^2 +17r^3 + . . . for 1<r<1-1 < r < 1. If S(a)×S(a)=2023S(a) \times S(-a) = 2023, find S(a)+S(a)S(a) + S(-a).