\[(a - 4)x > a² - 16\]
\[(a - 4)x > (a - 4)(a + 4)\]
\[a = 4 \Longrightarrow \ 0 \cdot x > 0,\ \ \ \varnothing\]
\[a < 4 \Longrightarrow \ \ x < a + 4\]
\[a > 4 \Longrightarrow x > a + 4\]