The function f(x)=x^3-3x is :

The correct answer is Option (4) → Increasing in $(-∞, -1] ∪ [1,∞)$ and decreasing in $(-1, 1)$

$f(x)=x^3-3x$

$f'(x)=3x^2-3=0⇒x=1,-1$

using wavy curve method

f(x) is increasing in $(-∞,-1]∪[1,∞)$

decreasing in $(-1, 1)$