A) (? 2, 3)
B) (2, 3)
C) (2,? 3)
D) None of these
Correct Answer: A
Solution :
\[f(x)=2{{x}^{3}}-3{{x}^{2}}-36x+7\] \[\Rightarrow f'(x)=6{{x}^{2}}-6x-36\] but for decreasing \[f'(x)<0\] Þ \[{{x}^{2}}-x-6<0\Rightarrow (x-3)(x+2)<0\] Þ \[-2<x<3\] Hence the required interval is (?2, 3).
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