Let ๐(๐) be the recurrence relation defined as follows: ๐(0) = 1, ๐(1) =โฆ
2024
Let ๐(๐) be the recurrence relation defined as follows:
ย ย ย ย ย ย ย ย ๐(0) = 1,
ย ย ย ย ย ย ย ย ๐(1) = 2, and
ย ย ย ย ย ย ย ย ๐(๐) = 5๐(๐ โ 1) โ 6๐(๐ โ 2) for ๐ โฅ 2
Which one of the following statements is TRUE?
- A.
๐(๐) = ฮ(2๐ )
- B.
๐(๐) = ฮ(๐2๐ )
- C.
๐(๐) = ฮ(3๐)
- D.
๐(๐) = ฮ(๐3๐)
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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) = Aยท2^n + Bยท3^n.
Use initial conditions: T(0)=1 โ A + B = 1; T(1)=2 โ 2A + 3B = 2.
Solve the system: subtracting 2ร(A + B = 1) from (2A + 3B = 2) gives B = 0, so A = 1.
Therefore T(n) = 2^n exactly, so T(n) = ฮ(2^n).
Conclusion: the recurrence solves to T(n) = 2^n, hence the correct growth is ฮ(2^n).
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