mong mn giúp đỡ với ạ :)))

`1) x^2- 4x^2y^2 + y^2 + 2xy`

`= (x^2+2xy+y^2) – 4x^2y^2`

`= (x+y)^2 – 4x^2y^2`

`2) (x+y)^3 -1-3xy.(x+y-1)`

`= (x+y)^3-1-3x^2y-3xy^2+3xy`

`= x^3+3x^2y+3xy^2+y^2-1-3x^2y-3xy^2+3xy`

`=x^3+y^2+3xy`

`3) x^3-1+5x^2-5+3x-3`

`= x^3-(1+3+5)+5x^2+3x`

`= x^3 + 5x^2+3x-9`

`4) a^5+a^4+a^3+a^2+a+1`

`= a(a^4+a^3+a^2+a+1)+1`

`5) x^3-3x^2+3x-1-y^3`

`=(x-1)^3-y^3 `