a,\(\frac{2018}{2015}\)và \(\frac{2019}{2020}\)
Ta có : \(\frac{2018}{2015}>0\)(vì 2018>2015)\(\)
\(\frac{2019}{2020}< 0\)(vì 2019<2020)
\(\Rightarrow\frac{2018}{2015}>\frac{2019}{2020}\)
b, MC : 97\(\cdot89\)
Ta có : \(\frac{2018}{97}=\)\(\frac{2018\cdot89}{97\cdot89}\)
\(\frac{2020}{89}=\frac{2020\cdot97}{97\cdot89}\)
Ta thấy : \(2018\cdot89< 2020\cdot97\)(vì 2018<2020;89<97)
\(\Rightarrow\frac{2018}{97}< \frac{2020}{89}\)