Applications Of Derivatives Question 262
Question: If $ f(x)=x^{3}-6x^{2}+9x+3 $ be a decreasing function, then x lies in
[RPET 2002]
Options:
A) $ (-\infty ,-1)\cap (3,,\infty ) $
B) $ (1,3) $
C) $ (3,\infty ) $
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
$ f(x)=x^{3}-6x^{2}+9x+3 $ , For decreasing $ {f}’(x)<0 $
therefore $ 3x^{2}-12x+9<0 $
therefore $ x^{2}-4x+3<0 $
therefore $ (x-3)(x-1)<0 $ , \ $ x\in (1,,3) $ .
BETA
