GATE CSE 2025 Session 2 Q8: Recurrences that generate the X and Y output rows

Which one of the following options is correct for the given data in the table?

Iteration $(i)$	0	1	2	3
Input $(I)$	20	$-4$	10	15
Output $(X)$	20	16	26	41
Output $(Y)$	20	$-80$	$-800$	$-12000$

Try it: multiple choice: exactly one correct option

Wrong answer costs 2/3 mark in GATE.

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Answer: A (official GATE 2025 final answer key)

Concept used: Identify a recurrence by checking it against consecutive columns of data.

First step: Check $i = 1$ : $20 + (-4) = 16$ for X and $20 \times (-4) = -80$ for Y, then confirm on $i = 2, 3$ .

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Source: official GATE 2025 Session 2 CS question paper and final answer key, organised by IIT Roorkee. Question paper · Answer key