先化简，再求值：（x+y）2﹣2y（x+y），其中x= 2−1 ，y= 3 ．_刷题宝

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先化简，再求值：（x+y）²﹣2y（x+y），其中x= 2−1 ，y= 3 ．

上一题下一题 0.0难度选择题更新时间:2019-03-06 02:08:37

答案(点此获取答案解析）

解：原式=x²+2xy+y²﹣2xy﹣2y²=x²﹣y²

当x= 2 ﹣1，y=

\sqrt{}

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