\[(a - 5)x \leq a^{2} - 25\]
\[(a - 5)x \leq (a - 5)(a + 5)\]
\[a = 5,\]
\[0 \cdot x \leq 0 \Longrightarrow \ ( - \infty;\ + \infty)\]
\[a < 5,\ \ x \geq a + 5\]
\[a > 5,\ \ x \leq a + 5.\]