`1/2+1/(2.3)+1/(3.4)+...... +1/(2021.2022)`
`=1/(1.2) +1/(2.3)+1/(3.4)+...... +1/(2021.2022)`
`=1-1/2+1/2-1/3+.......+1/2021-1/2022`
`=1-1/2022`
`=2022/2022-1/2022`
`=2021/2022`
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{2021}-\dfrac{1}{2022}\)
=1-1/2022
=2021/2022