Ta có : \(\dfrac{2018}{2019}-\dfrac{2017}{2018}=\dfrac{2018.2018-2019.2017}{2018.2019}\)
\(=\dfrac{2018.2018-\left(2018+1\right).\left(2018-1\right)}{2018.2019}\)
\(=\dfrac{2018.2018-2018.2018+2018-2018+1}{2018.2019}\)
\(=\dfrac{1}{2018.2019}=\dfrac{1}{4074342}\)
\(\dfrac{2018}{2019}-\dfrac{2017}{2018}\)=\(\dfrac{1}{4074342}\)