若x、y满足x^2+2y^2-2xy-2y+1=0,求xy的值
要过程,越详细越好
x^2+2y^2-2xy-2y+1=x^2-2xy+y^2+y^2-2y+1=(x-y)^2+(y-1)^2=0
所以Y=1 X=1
xy=1