Đáp án:
Giải thích các bước giải:
a) `(5x-2y)(x^2-xy+1)`
`=5x.x^2-5x.xy+5x-2x^2 . y-2y.(-xy)-2y`
`=5x^3-5x^2 y+5x-2x^2 y+2xy^2-2y`
`=5x^3-7x^2 y-2xy^2+5x-2y`
b) `(x-1)(x+1)(x+2)`
`=(x^2-x+x-1)(x+2)`
`=(x^2-1)(x+2)`
`=x^3+2x^2-x-2`
c) `12x^2 y^2 (2x+y)(2x-y)`
`= 12x^2 y^2 (4x^2-2xy+2xy+y^2)`
`=12x^2 y^2 (4x^2+y^2)`
`=12x^2 y^2 . 4x^2+12x^2 y^2 . y^2`
`=48x^4 y^2+48x^2 y^4`
