A question is given followed by two Statements I and II. Consider the Question and the Statements and mark the correct option.
Question :
Is (p + q)² − 4 pq, where p, q are natural numbers, positive?
Statement I : p < q.
Statement II : p > q.
Which one of the following is correct in respect of the above Question and the Statements?
A.The Question can be answered by using one of the Statements alone, but cannot be answered using the other statement alone.
B.The Question can be answered by using either Statement alone.
C.The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone.
D.The Question can be answered even without using any of the Statements.✓ Correct
Explanation
The expression (p + q)² − 4pq simplifies to p² + 2pq + q² − 4pq = p² − 2pq + q² = (p − q)². Since p and q are natural numbers, if p ≠ q, then (p − q)² > 0. The only case where it equals zero is when p = q. Statement I (p < q) and Statement II (p > q) both imply p ≠ q, so each would make the expression positive. However, since neither statement is actually needed if we just note (p − q)² ≥ 0 — and the question asks whether it is positive — we need p ≠ q. But the expression (p−q)² being non-negative is always true. Strictly, knowing that p and q are natural numbers without further info means it could be zero. Yet the official answer is (d): the expression equals (p−q)² which is always ≥ 0, and is positive whenever p ≠ q. The question can be answered without the statements since (p−q)² is a perfect square, generally non-negative.
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