\[x² + 11x = 0\]
\[x(x + 11) = 0\]
\[x = 0\ \ \ \ \ \ \ \ \ \ \ x + 11 = 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = - 11\]
\[Ответ:x = 0;\ x = - 11.\]