已知xy+x-y+1=6,(1-x²)(1-y²)+4xy=48 求xy-x+y+1的值

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已知xy+x-y+1=6,(1-x²)(1-y²)+4xy=48 求xy-x+y+1的值
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已知xy+x-y+1=6,(1-x²)(1-y²)+4xy=48 求xy-x+y+1的值
已知xy+x-y+1=6,(1-x²)(1-y²)+4xy=48 求xy-x+y+1的值

已知xy+x-y+1=6,(1-x²)(1-y²)+4xy=48 求xy-x+y+1的值
(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
即48=6(xy-x+y+1)
xy-x+y+1=8

48/6=8
(xy+x-y+1)*(xy-x+y+1)=(1-x²)(1-y²)