\[y = - 2x^{2} - 3x + a\]
\[D = 3^{2} - 4 \cdot ( - 2) \cdot a = 9 + 8a\]
\[9 + 8a < 0\]
\[8a < - 9\]
\[a < - 1\frac{1}{8}\]
\[Ответ:при\ a < - 1\frac{1}{8}.\]