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

Which of the following sequences aₙ is a solution of the recurrence relation aₙ = 8aₙ₋₁ − 16aₙ₋₂?
A. aₙ = 1
B. aₙ = 2ⁿ
C. aₙ = 4ⁿ
D. aₙ = n·4ⁿ
E. aₙ = (−4)ⁿ
Choose the most appropriate answer from the options given below:

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Correct answer: C. C, D Only

Explanation

The characteristic equation r² − 8r + 16 = 0 has the double root 4, so the general solution is (c₁ + c₂n)4ⁿ. 4ⁿ and n·4ⁿ satisfy it; 1, 2ⁿ and (−4)ⁿ do not.

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