\[ax + 3a = - 3 - x\]
\[ax + x = - 3a - 3\]
\[x(a + 1) = - 3 \bullet (a + 1)\]
\[a = - 1 \Longrightarrow x - любое.\]
\[Ответ:a \in ( - \infty;\ - 1) \cup ( - 1;\ + \infty).\]