Đáp án:
`T= 2/2 + 3/2^2 + ... + 2021/2^2020`
`=>2T=2+3/2+.....+2021/2^2020`
`=>2T-T=T=1+1/2+1/3^2+.....+1/2^2020-2021/2^2020`
`=>T<\underbrace{1+1/2+1/2^2+.....+1/2^2020}_{B}`
`2B=2+1/2+........+1/2^2019=>2B-B=B=2-1/2^2020<2`
`=>B<2`
Mà `T<B`
`=>T<B<2<3`