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CUET · MATHS · PYQ PAPER 2023

The interval where the function \(f(x)=2 x^3-9 x^2+12 x+15\) is decreasing, is :

  1. A \([1,2]\)
  2. B \((-\infty, 1] \cup[2, \infty)\)
  3. C \((-\infty, 2)\)
  4. D \((2, \infty)\)
Verified Solution

Answer & Solution

Correct Answer

(A) \([1,2]\)

Step-by-step Solution

Detailed explanation

\(f'(x) = 6x^2 - 18x + 12\) \(6x^2 - 18x + 12 \le 0\) \(x^2 - 3x + 2 \le 0\) \((x-1)(x-2) \le 0\) \(1 \le x \le 2\) The function is decreasing on \([1,2]\).
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