Let π(π) be the recurrence relation defined as follows: π(0) = 1, π(1) =β¦
2024
Let π(π) be the recurrence relation defined as follows:
Β Β Β Β Β Β Β Β π(0) = 1,
Β Β Β Β Β Β Β Β π(1) = 2, and
Β Β Β Β Β Β Β Β π(π) = 5π(π β 1) β 6π(π β 2) for π β₯ 2
Which one of the following statements is TRUE?
Answer: A. π(π) = Ξ(2π ) β Key idea: solve the recurrence by the characteristic equation. Form the characteristic equation: r^2 - 5r + 6 = 0, which has roots r = 2 and r = 3. Write theβ¦
- A.
π(π) = Ξ(2π )
- B.
π(π) = Ξ(π2π )
- C.
π(π) = Ξ(3π)
- D.
π(π) = Ξ(π3π)
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Correct answer: A
Key idea: solve the recurrence by the characteristic equation.
Form the characteristic equation: r^2 - 5r + 6 = 0, which has roots r = 2 and r = 3.
Write the general solution: T(n) = AΒ·2^n + BΒ·3^n.
Use initial conditions: T(0)=1 β A + B = 1; T(1)=2 β 2A + 3B = 2.
Solve the system: subtracting 2Γ(A + B = 1) from (2A + 3B = 2) gives B = 0, so A = 1.
Therefore T(n) = 2^n exactly, so T(n) = Ξ(2^n).
Conclusion: the recurrence solves to T(n) = 2^n, hence the correct growth is Ξ(2^n).
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