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已知x=1-根号2,y=根号2+1,求-x^2+2xy-y^2的值
人气:444 ℃ 时间:2020-04-03 23:00:10
解答
-x^2+2xy-y^2
=-(x^2-2xy+y^2)
=-(x-y)^2
=-(1-根号2-根号2-1)^2
=-(-2根号2)^2
=-8
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