ta có :  A= \(\dfrac{352}{353}+\dfrac{353}{354}+\dfrac{354}{355}\) 
ta có : B=\(\dfrac{352+353+354}{353+354+355}\)
=>       B=\(\dfrac{352}{353+354+355}+\dfrac{353}{353+354+355}\)+\(\dfrac{354}{353+354+355}\)
mà    \(\dfrac{352}{353+354+355}< \dfrac{352}{353}\)
rồi tự tính

có 1 thôi đúng ko

1

\(\dfrac{1+\dfrac{1}{3}+\dfrac{1}{5}+...+\dfrac{1}{2013}+\dfrac{1}{2015}}{\dfrac{1}{1.2015}+\dfrac{1}{3.2013}+\dfrac{1}{5+2011}+...+\dfrac{1}{2013.3}+\dfrac{1}{2015.1}}\)

Tính nhanh (10^2+11^2+12^2)+(13^2+14^2)