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CUET · MATHS · PYQ PAPER 2023

In the interval [-5, -3], the function f(x) = (x + 1)(x - 3) is:

  1. A strictly increasing
  2. B strictly decreasing
  3. C neither increasing nor decreasing
  4. D first increasing then decreasing
Verified Solution

Answer & Solution

Correct Answer

(B) strictly decreasing

Step-by-step Solution

Detailed explanation

\(f(x) = x^2 - 2x - 3\) \(f'(x) = 2x - 2\) For \(x \in [-5, -3]\): \(2x \in [-10, -6]\) \(f'(x) = 2x - 2 \in [-12, -8]\) Since \(f'(x) < 0\) for all \(x \in [-5, -3]\), the function is strictly decreasing.
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