1/1×3+1/3×5+1/5×7+…+1/2019×2020×1 GIÚP MIK NHANH NHA CẢM ƠN NHIỀU

Đáp án:

`A=1010/2021`

Giải thích các bước giải:

`A=1/(1×3)+1/(3×5)+1/(5×7)+…+1/(2019×2021`
`2A=2/(1xx3)+1/(3xx5)+1/(5xx7)+…+1/(2019xx2021)`
`2A=1/1-1/3+1/3-1/5+1/5-1/7+…+1/2019-1/2021`
`2A=1/1-1/2021`
`2A=2021/2021-1/2021`
`2A=2020/2021`
`A=2020/2021:2`
`A=2020/2021 . 1/2`
`A=2020/4042`
`A=1010/2021`