Applications Of Derivatives Question 272
Question: $ 2x^{3}-6x+5 $ is an increasing function if
[UPSEAT 2003]
Options:
A) $ 0<x<1 $
B) $ -1<x<1 $
C) $ x<-1 $ or $ x>1 $
D) $ -1<x<-1/2 $
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Answer:
Correct Answer: C
Solution:
Let $ f(x)=2x^{3}-6x+5 $
therefore $ {f}’(x)=6x^{2}-6>0 $
therefore $ x^{2}-1>0 $
therefore $ (x-1) $
$ (x+1)>0 $
therefore $ x>1 $ or $ x<-1 $ .
BETA
