\[x^{2} - 6x + 5 < 0\]
\[x^{2} - 6x + 5 = 0\]
\[x_{1} + x_{2} = 6;\ \ x_{1} \cdot x_{2} = 5\]
\[x_{1} = 5;\ \ \ x_{2} = 1\]
\[(x - 5)(x - 1) < 0\]
\[Ответ:\ \ (1;5).\]