\[3x^{3} - 12x = 0\]
\[3x\left( x^{2} - 4 \right) = 0\]
\[3x(x - 2)(x + 2) = 0\]
\[x = 0;x = 2;x = - 2.\]
\[Ответ:x = 0;x = \pm 2.\]