5B. Rút gọn các biểu thức: a) A = (x y)^2 + 4xy; b) B = (6x 2)^2 + 4(3x - 1)(2 + y) + (y + 2)^2 c)C=(x - y)^2 + 2(x^2 - y^2 ) + (x + y)^2

`a,`

`A = (x-y)^2 + 4xy`

`A = x^2 - 2xy + y^2 + 4xy`

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

`A = (x+y)^2`

`b,`

`B = (6x-2)^2 + 4.(3x - 1)(2 + y) + (y + 2)^2`

`B = (6x-2)^2 + 2.(6x-2)(2+y)+(y+2)^2`

`B = (6x-2+y+2)^2`

`B = (6x+y)^2`

`c,`

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

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

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

`C=(2x)^2`

`C=4x^2`

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