Ai giúp mình làm baid nayd dk ạ?

`a)`

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

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

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

`b)`

`B = (x-1)^2 - (x+1)^2`

`= (x- 1 - x - 1)(x - 1 + x + 1)`

`= -2.2x`

`= -4x`

`c)`

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

`= x^2 - 4 + x^2 + 4x + 4`

`= 2x^2 + 4x`

`d)`

`D = (x-5)(x^2 + 5x + 25 - x^3)`

`= x^3 + 5x^2 + 25x - x^4 - 5x^2 - 25x - 125 + 5x^3`

`= -x^4 + 6x^3 - 125`

`@Dark`