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Unit 1 · Discrete Structures and Optimization Paper 2 CS · June 2024 (Cancelled)

If f(n) = 5f(n/2) + 3 and f(1) = 7, where n = 2ᴷ and K is a positive integer, then f(2ᴷ) =

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Correct answer: A. 5ᴷ(31/4) − 3/4

Explanation

Unrolling: f(2ᴷ) = 5ᴷ·f(1) + 3(1 + 5 + … + 5ᴷ⁻¹) = 7·5ᴷ + 3(5ᴷ − 1)/4 = 5ᴷ(7 + 3/4) − 3/4 = 5ᴷ(31/4) − 3/4.

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