已知xy+x-y+1=6,(1-x^2)(1-y^2)+4xy=48,求xy-x+y+1的值!一定要今天

来源：学生作业帮编辑：神马作文网作业帮分类：数学作业时间：2024/11/13 21:32:06

（1-x²)(1-y²)+4xy
=1-y²-x²+x²y²+4xy
=2xy-y²-x²+(1+xy)²
=-(x-y)²+(1+xy)²
=48
(xy+x-y+1)(xy-x+y+1)=(xy+1)²-(x-y)²=48
xy+x-y+1=6
∴6（xy-x+y+1）=48
xy-x+y+1=8

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