\(\Leftrightarrow x^4-x^3-2x^2-x^3+x^2+2x-x^2+x+2=0\)
\(\Leftrightarrow x^2\left(x^2-x-2\right)-x\left(x^2-x-2\right)-1\left(x^2-x-2\right)=0\)
\(\Leftrightarrow\left(x^2-x-1\right)\left(x^2-x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-x-1=0\\x^2-x-2=0\end{matrix}\right.\)