Thực hiện các phép tính sau: a. ( x/2 - 2y)2 b. (2x - y)2 c. (1/2 x - 4y)2 d. (x + y)2 + (x - y)2

`(x/2-2y)^2`=$\frac{x^2}{4}$-`2``.``x/2`.`2y`+`4y^2`=$\frac{x^2}{4}$-`2xy+4y²`

`(2x-y)²`=`4x²-2.2x.y+y²`=`4x²-4xy+y²`

`(1/2 x - 4y)^2`=$\frac{x^2}{4}$-`2`.$\frac{x}{2}$.`4y`+`16y^2`=$\frac{x^2}{4}$-`2xy+4y²`=$\frac{x^2}{4}$-`4xy+16y²`

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