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