先化简,再求值:[(x+y)(x-y)-(x-y)²+2y(x+y)]除4y,其中x=2,y=1

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先化简,再求值:[(x+y)(x-y)-(x-y)²+2y(x+y)]除4y,其中x=2,y=1
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先化简,再求值:[(x+y)(x-y)-(x-y)²+2y(x+y)]除4y,其中x=2,y=1
先化简,再求值:[(x+y)(x-y)-(x-y)²+2y(x+y)]除4y,其中x=2,y=1

先化简,再求值:[(x+y)(x-y)-(x-y)²+2y(x+y)]除4y,其中x=2,y=1
化简,得
[(x+y)(x-y)-(x-y)²+2y(x+y)]÷4y
=(x-y)[(x+y)-(x-y)+2y]÷4y
=(x-y)(x+y-x+y+2y)÷4y
=(x-y)*4y÷4y
=x-y
因为x=2,y=1
所以x-y=1
所以
[(x+y)(x-y)-(x-y)²+2y(x+y)]÷4y=1