<=>\(\left[{}\begin{matrix}x^2-1=2x+1\\x^2-1=-2x-1\end{matrix}\right.< =>\left[{}\begin{matrix}x^2-2x-2=0\\x^2+2x=0\end{matrix}\right.\)<=>\(\left[{}\begin{matrix}\left[{}\begin{matrix}1+\sqrt{3}\\1-\sqrt{3}\end{matrix}\right.\\\left[{}\begin{matrix}x=0\\x=-2\end{matrix}\right.\end{matrix}\right.\)