x^2+y^2+1.25=2x+y
x^2-2x+1+y^2-y+0.25=0
(x-1)^2+(y-0.5)^2=0
x=1,y=0.5.
xy/(x+y)=1*0.5/(1+0.5)=0.5/1.5=1/3