\[\frac{x + a}{a - 8} = 0;\ \ \ \ \ \ x \neq - 8\]
\[x + a = 0\]
\[x = - a.\]
\[a = - 8 \Longrightarrow нет\ решения.\]
\[a \neq - 8 \Longrightarrow x = - a.\]