So sánh : A=2017/2018 +2018/2019 và B =2017+2018 / 2018+2019

* Hướng dẫn giải

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