Đáp án+Giải thích các bước giải:
`2)x^2 (x-2019)-x+2019`
`=x^2 (x-2019) -(x-2019)`
`=(x^2 -1)(x-2019)`
`3)8x^2y-8x^3 -2xy^2 +18x`
`=2x(4xy -4x^2 -y^2 +9)`
`=2x[-(2x -y)^2 +9]`
`=2x[3^2 -(2x-y)^2]`
`=2x(3+2x-y)(3-2x+y)`
`4)x^3 -2x^2 +2x-1`
`=(x^3 -1)+(2x-2x^2)`
`=(x-1)(x^2 +x+1)+2x(1-x)`
`=(x-1)(x^2 +x+1 -2x)`
`=(x-1)(x^2 -x+1)`