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CUET · MATHS · PYQ PAPER 2025

If the interval in which the function \(f(x)=4 x^3-6 x^2-72 x+30\) is strictly decreasing, is \(( a , b )\) then \(a + b\) is equal to

  1. A \(\infty\)
  2. B \(0\)
  3. C 1
  4. D 2
Verified Solution

Answer & Solution

Correct Answer

(C) 1

Step-by-step Solution

Detailed explanation

\(f'(x) = 12x^2 - 12x - 72\) \(12x^2 - 12x - 72 \(x^2 - x - 6 \((x-3)(x+2) \(x \in (-2, 3)\) \(a = -2, b = 3\) \(a+b = -2 + 3 = 1\)
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