甲买米均价X=(100a+100b)/200=(a+b)/2
乙买米均价Y=200/[(100/a)+(100/b)]=200ab/(100a+100b)=2ab/(a+b)
X-Y=[(a+b)^2-4ab]/2(a+b)=(a^2-2ab+b^2)/2(a+b)=(a-b)^2/2(a+b)
因为(a-b)^2>0,a+b>0,所以X-Y>0,所以X>Y,即乙的买米均价低些
甲买米均价X=(100a+100b)/200=(a+b)/2
乙买米均价Y=200/[(100/a)+(100/b)]=200ab/(100a+100b)=2ab/(a+b)
X-Y=[(a+b)^2-4ab]/2(a+b)=(a^2-2ab+b^2)/2(a+b)=(a-b)^2/2(a+b)
因为(a-b)^2>0,a+b>0,所以X-Y>0,所以X>Y,即乙的买米均价低些