\[x^{3} - 4x = 0\]
\[x\left( x^{2} - 4 \right) = 0\]
\[x(x - 2)(x + 2) = 0\]
\[x = 0;x = 2;x = - 2.\]
\[Ответ:числа\ \ 0;\ - 2;\ \ 2.\]