\(\left\{{}\begin{matrix}\Delta=b^2-4c>0\\x_1x_2=c=1\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}b^2-4>0\\c=1\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}b^2>4\\c=1\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}b>2\\b< -2\end{matrix}\right.\\c=1\end{matrix}\right.\)