Applications Of Derivatives Question 393
Question: The interval for which the given function $ f(x)=2x^{3}-3x^{2}-36x+7 $ is decreasing, is
Options:
A) (- 2, 3)
B) (2, 3)
C) (2,- 3)
D) None of these
Show Answer
Answer:
Correct Answer: A
Solution:
$ f(x)=2x^{3}-3x^{2}-36x+7 $
$ \Rightarrow f’(x)=6x^{2}-6x-36 $ but for decreasing $ f’(x)<0 $
therefore $ x^{2}-x-6<0\Rightarrow (x-3)(x+2)<0 $
therefore $ -2<x<3 $
Hence the required interval is (-2, 3).
BETA
