Applications Of Derivatives Question 270

Question: The function $ f(x)=1-x^{3}-x^{5} $ is decreasing for

[Kerala (Engg.) 2002]

Options:

A) $ 1\le x\le 5 $

B) $ x\le 1 $

C) $ x\ge 1 $

D) All values of x

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Answer:

Correct Answer: D

Solution:

$ f(x)=1-x^{3}-x^{5} $

therefore $ {f}’(x)=-3x^{2}-5x^{4} $

$ {f}’(x)<0 $ for all values of x.