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TS EAMCET · Maths · Application of Derivatives

For a real number ' \(a\) ', if a real valued function \(f(x)=4 x^3+a x^2+3 x-2\) is monotonic in its domain, then the range of ' \(a\) ' is

  1. A (-6,6)
  2. B Empty set
  3. C (-2,2)
  4. D (2,4)
Verified Solution

Answer & Solution

Correct Answer

(A) (-6,6)

Step-by-step Solution

Detailed explanation

\(f'(x) = 12x^2 + 2ax + 3\) For monotonicity, \(D \le 0\) \((2a)^2 - 4(12)(3) \le 0\) \(4a^2 - 144 \le 0\) \(a^2 \le 36\) \(-6 \le a \le 6\)