Đáp án:
`a, 8x^3 - y^3 - 6xy(2x - y)`
`= (2x)^3 - y^3 - 6xy(2x - y)`
`= (2x - y)(4x^2 + 2xy + y^2) - 6xy(2x - y)`
`= (2x - y)(4x^2 + 2xy - 6xy + y^2)`
`= (2x - y)(4x^2 - 4xy + y^2)`
`= (2x - y)[(2x)^2 - 2.2x.y + y^2]`
`= (2x - y)(2x - y)^2`
`= (2x - y)^3`
C2: ` a, 8x^3 - y^3 - 6xy(2x - y)`
`= 8x^3 - 12x^2 y + 6xy^2 - y^3`
`= (2x)^2 - 3.(2x)^2 .y + 3.2x.y^2 - y^3`
`= (2x - y)^3`
`b, (3x + 2)^2 - 2.(x -1)(3x + 2) + (x - 1)^2`
`= [(3x + 2) - (x - 1)]^2`
`= (3x + 2 - x + 1)^2`
`= (2x + 3)^2`
