(b+m)/(a+m)-b/a=a(b+m)/[a(a+m)]-b(a+m)/[a(a+m)]=(ab+am-ab-bm)/[a(a+m)]=m(a-b)/[a(a+m)]a>b>0 m>0所以a(a+m)>0a-b>0得上式>0所以(b+m)/(a+m)大于b/a
