已知xy=3,x^2+xy-2y^2=2(x+2y),则x+y= 最好写出计算过程

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已知xy=3,x^2+xy-2y^2=2(x+2y),则x+y=最好写出计算过程已知xy=3,x^2+xy-2y^2=2(x+2y),则x+y=最好写出计算过程已知xy=3,x^2+xy-2y^2=2

已知xy=3,x^2+xy-2y^2=2(x+2y),则x+y= 最好写出计算过程
已知xy=3,x^2+xy-2y^2=2(x+2y),则x+y= 最好写出计算过程

已知xy=3,x^2+xy-2y^2=2(x+2y),则x+y= 最好写出计算过程
x²+xy-2y²=2(x+2y)
x²+(y-2)x-2y²-4y=0
x²+(y-2)x-2y(y+2)=0
(x+2y)(x-y-2)=0
解得x=-2y舍或x=y+2
又xy=3解得x=-1,y=-3或x=3,y=1
所以x+y=-4或x+y=4

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