Find Where Increasing/Decreasing f(x)=x^3-4x

Graph the polynomial in order to determine the intervals over which it is increasing or decreasing.

Increasing on: ${\displaystyle (-\infty ,-\frac{2\sqrt{3}}{3}),(\frac{2\sqrt{3}}{3},\infty )}$

Decreasing on: ${\displaystyle (-\frac{2\sqrt{3}}{3},\frac{2\sqrt{3}}{3})}$