\[\left\{ \begin{matrix} 1 > 0 \\ D < 0 \\ \end{matrix} \right.\ \]
\[= 12a^{2} - 40a + 12 < 0\]
\[12a² - 40a + 12 < 0\ \ \ |\ :4\]
\[3a^{2} - 10a + 3 = 0\]
\[D = 100 - 36 = 64\]
\[a_{1} = \frac{10 + 8}{6} = 3\]
\[a_{2} = \frac{10 - 8}{6} = \frac{1}{3}\]
\[\left( a - \frac{1}{3} \right)(a - 3) < 0\ \]
\[\frac{1}{3} < a < 3.\]
\[Ответ:\left( \frac{1}{3};3 \right).\]