\[= - 4a^{2} - 24a - 36 =\]
\[= - 4 \cdot \left( a^{2} + 6a + 9 \right) =\]
\[= - 4 \cdot (a + 3)^{2}\]
\[- 4 \cdot (a + 3)^{2} > 0\]
\[Ответ:нет\ таких\ a.\]