\[a^{\backslash a^{2} - 16} - \frac{a^{3} - 15a - 4}{a^{2} - 16} =\]
\[= \frac{a\left( a^{2} - 16 \right) - a^{3} + 15a + 4}{a^{2} - 16} =\]
\[= \frac{a^{3} - 16a - a^{3} + 15a + 4}{a^{2} - 16} =\]
\[= \frac{4 - a}{(a - 4)(a + 4)} =\]
\[= - \frac{(a - 4)}{(a - 4)(a + 4)} =\]
\[= - \frac{1}{a + 4};\ \ \ \ \ \ \ \ \]
\[a = - 4,5:\]
\[- \frac{1}{- 4,5 + 4} = \frac{- 1}{- 0,5} = 2.\]