\left\{ \begin{array}{l}\Delta = b^2 - 4ac > 0 \\ x_1 x_2 = c = 1 \\ \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}b^2 > 4 \\ c = 1 \\ \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}b < 2,b > - 2 \\ c = 1 \\ \end{array} \right.