x²y²-8xy+4x²+y²+4=0x²y²-4xy+4+4x²-4xy+y²=0(xy-2)²+(2x-y)²=0平方项恒非负,两平方项之和=0,两项分别=0xy-2=0 xy=22x-y=0 y-2x=0y-2x+(yx/2)^2013=0+(2/2)^2013...