Thực hiện phép tính (x - 1)(x^2 - x + 1) - (x - x^2)(2x)

Ta có: x−1x2−x+1−x−x22x

                =x2x−1−xx−1+1x−1−x.2x−x2.2x

                =x.x2−1.x2−x.x−1.x+x−1−2x2−2x3

                =x3−x2−x2+x+x−1−2x2+2x3

                =3x3−4x2+2x−1