已知x^2+4y^2-2x+4y+2=0求（xy-x^2)/(x^2-2xy+y^2)/xy的值
问题描述：
已知x^2+4y^2-2x+4y+2=0求（xy-x^2)/(x^2-2xy+y^2)/xy的值
答
x^2+4y^2-2x+4y+2=0(x^2-2x+1)+(4y^2+4y+1)=0(x-1)^2+(2y+1)^2=0平方大于等于0,相加等于0,若有一个大于0,则另一个小于0,不成立.所以两个都等于0所以x-1=0,2y+1=0x=1,y=-1/2(xy-x^2)/[(x^2-2xy+y^2)/xy]=xy(xy-x^2)/(...