`x^3 -x^2 -x+1=0`
`x^2(x-1) -(x-1) =0`
`(x^2-1)(x-1) =0`
`TH1 : x^2 -1 =0 <=> x^2 =1 <=> x=+-1`
`Th2 : x-1 =0 => x=1`
`=> x = +-1`
Vậy `x=+-1`
`x^3 -x^2 -x+1=0`
`<=>x^2(x-1)-(x+1)=0`
`<=>x^2(x-1)-(x-1)=0`
`<=>(x-1)(x^2-1)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x^2-1=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0+1\\x^2=1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=\pm1\end{matrix}\right.\)
\(< =>x^2\left(x-1\right)-\left(x-1\right)=0< =>\left[{}\begin{matrix}x^2-1=0\\x-1=0\end{matrix}\right.< =>x=1}\)
