Xét tích: a(b+2001) = ab + 2001a
b(a+2001) = ab + 2001b. Vì b > 0 nên b + 2001 > 0
*Nếu a > b thì ab + 2001a > ab + 2001b
a(b + 2001) > b(a + 2001)
=> \(\dfrac{a}{b}\) > \(\dfrac{a+2001}{b+2001}\)
*Tương tự nếu a < b thì => \(\dfrac{a}{b}\) < \(\dfrac{a+2001}{b+2001}\)
*Và nếu a = b thì => \(\dfrac{a}{b}\)=\(\dfrac{a+2001}{b+2001}\)