So sánh: 

- Hướng dẫn giải

Ta có

$A=\frac{2017}{2018}+\frac{2018}{2019}>\frac{2017}{2019}+\frac{2018}{2019}=\frac{2018+2018}{2019}$

Mà $\frac{2017+2018}{2019}>\frac{2017+2018}{2018+2019}=B$

Nên A > B