a: Tọa độ giao điểm là:
\(\left\{{}\begin{matrix}x^2-x-1=x-1\\y=x-1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\left(x-2\right)=0\\y=x-1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\in\left\{0;2\right\}\\y\in\left\{-1;1\right\}\end{matrix}\right.\)