\[3x^{3} - 108x = 0\]
\[3x\left( x^{2} - 36 \right) = 0\]
\[3x(x - 6)(x + 6) = 0\]
\[3x = 0;\ \ \ \ \ \ x - 6 = 0;\ \ \ \ \ x + 6 = 0\]
\[x = 0\ \ \ \ \ \ \ \ \ \ x = 6\ \ \ \ \ \ \ \ \ \ \ \ \ \ x = - 6\]
\[Ответ:x = \pm 6;\ \ x = 0.\]