计算：(x+y)²-(x-y)²＝

计算：(x+y)²-(x-y)²＝
计算：(x+y)²-(x-y)²＝

计算：(x+y)²-(x-y)²＝
(x+y)²-(x-y)²
=[(x+y)-(x-y)][(x+y)+(x-y)]
=(x+y-x+y)(x+y+x-y)
=2y*2x
=4xy

(x+y)²-(x-y)²
=(x+y+x-y)(x+y-x+y)
=2x*2y
=4xy

(x+y)²-(x-y)²
=X方+2xy+y方-(X方-2xy+y方)
=X方+2xy+y方-X方+2xy-y方
=4xy
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