Đáp án:

Giải thích các bước giải:

 TA có:

Đặt `A=4/1.3-8/3.5+12/5.7-16/7.9+...+100/49.51-104/51.53`

`=>A=(1/1+1/3)-(1/3+1/5)+(1/5+1/7)-(1/7+1/9)+...+(1/49+1/51)-(1/51+1/53)`

`=>A=1/1+1/3-1/3-1/5+1/5+1/7-1/7-1/9+...+1/49+1/51-1/51-1/53`

`=>A=1/1-1/53`

`=>A=53/53-1/53`

`=>A=52/53`

Vậy `A=52/53`