xˇ2--2xy+yˇ2-4x+y-15=0
(x-y)ˇ2-4x+y-15=0
x=2y-1,带入得
(y-1)ˇ2-4(2y-1)-15=0
(y-10)(y+1)=0得,y=10或y=-1
x=19,y=10或x=-3,y=-1