（x-1)(y+1)
=xy+x-y-1
=根号2+根号2-1-1
=2（根号2-1）
祝学习进步
解：由题 x-y=√2-1
xy=√2
（x-1)(y+1)=xy+(x-y)-1
=√2-1+ √2-1
=2√2-2
若x+y=根号2-1,xy=根号2,则
代数式
(x-1)(y-1)的值等于?
(x-1)(y-1)
=xy-x-y+1
=xy-(x+y)+1
=根号2-根号2+1+1
=2
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