\(\sqrt[3]{x^3-4x}=0\Leftrightarrow x^3-4x=0\Leftrightarrow x\left(x^2-4\right)=0\Leftrightarrow x\left(x-2\right)\left(x+2\right)=0\Leftrightarrow\left[{}\begin{matrix}x=0\\x-2=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\pm2\end{matrix}\right.\)
Vậy \(S=\left\{0;\pm2\right\}\)