Q= 11/12+19/20+29/30+41/42+55/56+71/72+89/90+109/110

Đáp án: + Giải thích các bước giải:

`Q = 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90 + 109/110`

`= 1 - 1/12  + 1 - 1/20  + 1 - 1/30 + 1 - 1/42 + 1 - 1/56 + 1 - 1/72 + 1 - 1/90 + 1 - 1/110`

`= (1 + 1 + 1 + ... + 1 + 1) - ( 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90 + 1/110 )`

`= 8 - ( 1/3.4 + 1/4.5 + 1/5.6 + 1/6.7 + 1/7.8 + 1/8.9 + 1/9.10 + 1/10.11 )`

`= 8 - (1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 + 1/7 - 1/8 + 1/8 - 1/9 + 1/9 - 1/10 + 1/10 - 1/11 )`

`= 8 - (1/3 - 1/11)`

`= 8 - 8/33`

`= 264/33 - 8/33`

`= 256/33`