\[x² + x = 0\]
\[x(x + 1) = 0\]
\[x = 0\ \ \ \ \ \ \ \ \ \ x + 1 = 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = - 1\]
\[Ответ:x = 0\ \ и\ \ \ x = - 1.\]