\[\frac{x + 3}{x(x - 3)}\]
\[Не\ имеет\ смысла\ при\ \]
\[x(x - 3) = 0\]
\[x = 0\ \ \ \ \ \ \ x - 3 = 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = 3\]
\[Ответ:x = 0;\ \ x = 3.\]