\(\left|x^2-1\right|=2x+1\left(dk:2x+1\ge0\Leftrightarrow2x\ge-1\Leftrightarrow x\le-\dfrac{1}{2}\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-1=2x+1\\x^2-1=-2x-1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-1-2x-1=0\\x^2-1+2x+1=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-2x-2=0\\x^2+2x=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-2x-2+3=3\\x.\left(x+2\right)=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(x-1\right)^2=3\\\left[{}\begin{matrix}x=0\\x=-2\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(x-1^2\right)-\left(\sqrt{3}\right)^2=0\\\left[{}\begin{matrix}x=0\\x=-2\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(x-1-\sqrt{3}\right).\left(x-1+\sqrt{3}\right)=0\\\left[{}\begin{matrix}x=0\\x=-2\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}x=1-\sqrt{3}\left(loai\right)\\x=1+\sqrt{3\left(loai\right)}\end{matrix}\right.\\\left[{}\begin{matrix}x=0\left(loai\right)\\x=-2\left(tm\right)\end{matrix}\right.\end{matrix}\right.\)
Vậy x = -2