化简求值:[(x﹣y)(x+y)﹣(x﹣y)2+2y(x﹣y)]÷(﹣2y),其中x=﹣,y=2. ...

2023-07-08 17:48发布

这道初中数学的题目是:
化简求值:[(x﹣y)(x+y)﹣(x﹣y)2+2y(x﹣y)]÷(﹣2y),其中x=﹣,y=2.
1条回答
七上八下
2023-07-08 17:57
这道初中数学题的正确答案为:
解:[(x﹣y)(x+y)﹣(x﹣y)2+2y(x﹣y)]÷(﹣2y),
=[x2﹣y2﹣(x2﹣2xy+y2)+2xy﹣2y2]÷(﹣2y),
=(x2﹣y2﹣x2+2xy﹣y2+2xy﹣2y2)÷(﹣2y),
=(4xy﹣4y2)÷(﹣2y),
=﹣2x+2y,
当x=﹣,y=2时,
原式=﹣2x+2y=﹣2×(﹣)+2×2=1+4=5.
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