Giúp mik với Bài 2 nha

`A=1/1.2+1/3.4+1/5.6+...+1/99.100`

`=1-1/2+1/3-1/4+1/5-1/6+...+1/99-1/100`

`=1+1/3+1/5+...+1/99-(1/2+1/4+1/6+...+1/100)`

`=1+1/2+1/3+...+1/99+1/100-2.(1/2+1/4+1/6+...+1/100)` `(`cộng vào mối vế

`1/2+1/4+1/6+...+1/100`$)$

`=1+1/2+1/3+...+1/99+1/100-(1+1/2+1/3+...+1/50)`

`=1/51+1/52+1/53+...+1/100`

`⇒B=2017(1/51+1/52+1/53+...+1/100)`

`⇒B/A=2017∈\mathbbZ` `(đpcm)`