\[x^{3} - 9x = 0\]
\[x\left( x^{2} - 9 \right) = 0\]
\[x(x - 3)(x + 3) = 0\]
\[x = 0;x = 3;x = - 3.\]
\[Ответ:x = 0;x = \pm 3.\]