Ta có: \(A=2019.2021=\left(2020-1\right)\left(2020+1\right)=2020^2-1\)
\(B=2020^2\)
=> A < B
A=2019.2021
A=(2020-1)(2020+1)
A=2020²-1
Vậy: A<B
TA CÓ \(A=2019.2020\)
\(=\left(2020-1\right)\left(2020+1\right)\)
\(=2020^2-1\)
\(B=2020^2\)
\(\Leftrightarrow A\le B\)
HOK TỐT