\[x^{2} + 8ax - 15a + 1 = 0\]
\[D = 64a^{2} + 60a - 4 > 0\]
\[64a² + 60a - 4 > 0\ \ \ |\ :4\]
\[16a^{2} + 15a - 1 > 0\]
\[16a^{2} + 15a - 1 = 0\]
\[D = 225 + 64 = 289\]
\[a = \frac{- 15 + 17}{32} = \frac{1}{16}\]
\[a = \frac{- 15 - 17}{32} = - 1\]
\[Ответ:( - \infty; - 1) \cup \left( \frac{1}{16}; + \infty \right).\]