Let , where . Find all real values of for which has no local maximum or minimum on…

MATHEMATICS · Subjective · A Level · Mathematics · Differentiation · Differentiation

Problem

Let

f_a(x)=x^{3}+a x

, where

a\in\boldsymbol{\text{R}}

. Find all real values of

a

for which

f_a

has no local maximum or minimum on

\boldsymbol{\text{R}}