(x-y)^2-2(x-y)*(1/2)+(1/2)^2=0(x-y-1/2)^2=0x-y-1/2=0x-y=1/2
(x-y)^2-2(x-y)*(1/2)+(1/2)^2=[(x-y)-1/2]^2=0(x-y)-1/2=0x-y=1/2