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MHT CET202120 Sep 2021Evening ShiftMathematicsApplication of DerivativesActual

If f(x)=2 x^3-15 x^2-144 x-7 , then f(x) is strictly decreasing in

Options

  1. A(-8,3)
  2. B(-3,8)
  3. C(3,8)
  4. D(-8,-3)

Correct answer

B. (-3,8)

Step-by-step solution

aligned & f ( x )=2 x ^3-15 x ^2-144 x -7 & f ^ ( x )=6 x ^2-30 x -144 & When f ^ ( x ) < 0, we get x ^2-5 x -24 < 0 & ( x -8)( x +3) < 0 -3 < x < 8 aligned

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