\[x^{2} - 2ax + a^{2} - 1 = 0\]
\[D = {4a}^{2} - 4a^{2} + 4 = 4 > 0\]
\[x_{1} = \frac{2a + 2}{2} = a + 1\]
\[x_{2} = \frac{2a - 2}{2} = a - 1\]
\[\left\{ \begin{matrix} a + 1 > 3 \\ a - 1 > 3 \\ \end{matrix}\text{\ \ \ \ \ \ \ \ \ } \right.\ \]
\[\left\{ \begin{matrix} a > 2 \\ a > 4 \\ \end{matrix}\ \ \ \Longrightarrow \ a > 4 \right.\ \]
\[Ответ:\ \ (4;\ + \infty).\]