\(\dfrac{2021.2023-1}{2021.2022+2019}\)
\(=\dfrac{2021.2022+2021-1}{2019+2021.2022}\)
\(=\dfrac{2021.2022+2020}{2019+2021.2022}\)
\(=\dfrac{2021.2022+2019}{2019+2021.2022}+\dfrac{1}{2019+2021.2022}\)
\(=1+\dfrac{1}{2019+2021.2022}\)
\(\dfrac{2021.2023-1}{2019+2021.2022}\)
\(=\dfrac{2021.\left(2022+1\right)-1}{2019+2021.2022}\)
\(=\dfrac{2021.2022+\left(2021-1-1\right)}{2019+2021.2022}\)
\(=\dfrac{2021.2022+2019}{2019.2021.2022}\)\(=1\)