\[y = 4x^{2} - (3a + 2)x + a - 1;\ \ \]
\[x_{1} < 3 < x_{2}\]
\[\left\{ \begin{matrix} a > 0\ \ \ \ \ \\ f(3) < 0 \\ \end{matrix}\text{\ \ \ \ \ \ } \right.\ \]
\[f(3) = 36 - 9a - 6 + a - 1 < 0\]
\[- 8a < - 29\]
\[a > \frac{29}{8}\text{\ \ }\]
\[a > 3\frac{5}{8}\]
\[Ответ:при\ a \in \left( 3\frac{5}{8};\ \ + \infty \right).\]