有这样一道题“计算x2-2x+1x2-1÷x-1x2+x-x的值，其中x=2005”．甲同学把条件“x=2005”错抄成”x=2050“，但他的计算结果也是正确的，你说这是怎么回事？试一试，你就会有收

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