问题描述: 先化简,再求值:[(x+y)(x-y)-(x-y)²+2y(x+y)]除4y,其中x=2,y=1 1个回答 分类:综合 2014-12-11 问题解答: 我来补答 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 展开全文阅读