\[5a^{2} - 9a - 2 = 0\]
\[D = 81 + 40 = 121\]
\[a_{1} = \frac{9 + 11}{10} = 2;\ \ \ \ \]
\[a_{2} = \frac{9 - 11}{10} = - \frac{2}{10} = - \frac{1}{5}.\]
\[5a^{2} - 9a - 2 =\]
\[= 5 \cdot (a - 2)\left( a + \frac{1}{5} \right) =\]
\[= (a - 2)(5a + 1).\]