(x-y)分之x-(x+y)分之y+(x的2次方- - 知识问答

(x-y)分之x-(x+y)分之y+(x的2次方-y的2次方)分之2xy

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(x-y)分之x-(x+y)分之y+(x的2次方-y的2次方)分之2xy
=(x-y)分之x-(x+y)分之y+(x-y)(x+y)分之2xy
=(x-y)(x+y)分之[x(x+y)-y(x-y)+2xy]
=(x-y)(x+y)分之(x平方＋2xy＋y平方)
=(x-y)(x+y)分之(x+y)平方
=(x-y)分之(x+y)

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