x²+y²+5/4=x-2y
x²-x+y²+2y+5/4=0
(x²-x+1/4)+(y²+2y+1)=0
(x-1/2)²+(y+1)²=0
∴x-1/2=0,y+1=0
∴x=1/2,y=-1
∴2x+y
=2*1/2+(-1)
=1-1
=0