question_answer

Let \[f;[-1,3]\to [-8,\,72]\] be defined as \[f(x)=4{{x}^{3}}-12x\],then \[f\] is

A)  injective but not surjective

B)  injective as well as surjective

C)  neither injective nor surjective

D)  surjective but not injective

Correct Answer: D

Solution :

\[f(x)=4{{x}^{3}}-12x\]