猜若实数x，y满足x +y=1,y=1-x,2y·y-x·x-m=0，m=2y^2-x^2=2(1-x)^2-x^2=2(1-2x+x^2)-x^2=x^2-4x+2=(x-2)^2-2,当x=2时取最小值-2.
