Đáp án + Giải thích các bước giải:
`(x+1)³-(x-1)(x²+x+1)-3x(x+1)`
`= (x+1)[(x+1)²-(x²+x+1)-3x]`
`= (x+1)[x²+2x+1-x²-x-1-3x]`
`= (x+1).(-2x)`
`= -2x²-2x`
`(x+2y)(x²-2xy+4y²)-(x-2y)(x²+2xy+4y²)+2y³`
`= x³+(2y)³-x³+(2y)³+2y³`
`= 8y³+8y³+2y³`
`= 18y³`
`(x-2)³-x(x+1)(x-1)+6x(x-3)`
`= x³-6x²+12x-2³-x(x²-1)+6x²-18x`
`= x³-6x²+12x-8-x³+x+6x²-18x`
`= -5x-8`