`S= 1/2022 - 5/2.4 - 5/4.6 -...-5/2020.2022`
`S= 1/2022 - ( 5/2.4 + 5/4.6 +...+5/2020.2022)`
Đặt `A= 5/2.4 + 5/4.6 +...+ 5/2020.2022`
`A: 5 = 1/2.4 + 1/4.6 +...+1/2020.2022`
`A : 5.2 = 2/2.4 + 2/4.6 +...+2/2020.2022`
`A: 5.2 = 1/2-1/4 +1/4-1/6 +...+1/2020 - 1/2022`
`A:5 .2 = 1/2 - 1/2022`
`A = 505/1011`
`A = 505/1011 : 2 .5`
`A=2525/2022`
`=> S= 1/2022 - 2525/2022`
`=> S= -1262/1011`
Vậy `S= -1262/1011`
