Đáp án `+`Giải thích các bước giải:

`1) (x^2y^2 + 1/6x^3y^2 - x^5y^4) : 1/2 xy^2`

`= x^2y^2 : 1/2 xy^2 + 1/6 x^3y^2 : 1/2 xy^2 - x^5y^4 : 1/2 xy^2`

`= (1 : 1/2)(x^2 : x)(y^2 : y^2) + (1/6 : 1/2) (x^3 : x)(y^2 : y^2) + (-1 : 1/2)(x^5 : x)(y^4 : y^2)`

`= 2x +1/3x^2 - 2x^4y^2`

`2) (x-y)(x+y) (x+2)`

`= (x^2 - y^2) (x+2)`

`= x(x^2 - y^2) + 2 (x^2 - y^2)`

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

`3) (x-y) (x-y) + (x+y)(x+y)`

`= (x-y)^2 + (x+y)^2`

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

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

`= 2x^2 + 2y^2`