`a)`
`-(2021)/(2020)<0`
`(1)/(2)>0`
`->(1)/(2)> -(2021)/(2020)`
`b)`
`(2022)/(2021)=1+(1)/(2021)`
`(2021)/(2020)=1+(1)/(2020)`
Vì `(1)/(2021)<(1)/(2020)`
`->1+(1)/(2021)<1+(1)/(2020)`
`->(2022)/(2021)<(2021)/(2020)`
a: \(-\dfrac{2021}{2020}< 0\)
\(0< \dfrac{1}{2}\)
Do đó: \(-\dfrac{2021}{2020}< \dfrac{1}{2}\)
b: \(\dfrac{2022}{2021}=1+\dfrac{1}{2021}\)
\(\dfrac{2021}{2020}=1+\dfrac{1}{2020}\)
mà \(\dfrac{1}{2021}< \dfrac{1}{2020}\)
nên \(\dfrac{2022}{2021}< \dfrac{2021}{2020}\)