Let T(n) be the recurrence relation defined as follows: T(0) = 1, T(1) = 2, and T(n) = 5T(n - 1) - 6T(n - 2) for n ≥ 2 Which one of the following statements is TRUE?
Topic-wise GATE CS PYQs with verified steps
GATE CSE 2024 Set 2 · Q15
Time
Select one answerSingle correct
Solution
Official answer: A) T(n) = (2n)
Recurrence RelationsTo solve the linear homogeneous recurrence relation with constant coefficients:
The characteristic equation is:
The general solution is:
Using the given initial conditions:
For $n = 0$: $T(0) = c_1 + c_2 = 1$
For $n = 1$: $T(1) = 2c_1 + 3c_2 = 2$
Multiplying the first equation by and subtracting from the second:
Substituting into gives .
Therefore, the closed-form solution is:
Hence, , which corresponds to (A).
Try the question first, then check your work.
Examiner trap
Form the characteristic equation to find the roots, write the general form , and solve for the constants using the base cases.
This Recurrence Relations previous year question is Q15 of the GATE CSE 2024 Set 2 paper. Find more GATE CSE PYQs on Recurrence Relations in Engineering Mathematics, or browse all GATE CSE PYQs.
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Recurrence Relations has 4 GATE CSE PYQs across 4 papers from 2016 to 2024. 3 of them are 1-mark MCQs like this one, and it is the only one in GATE CSE 2024 Set 2.
How GATE tests Recurrence RelationsIndependent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.