Đáp án:
Giải thích các bước giải:
` (1/2+1)(1/3+1)(1/4+1)...(1/2017+1)(1/2018 +1)`
đặt` C= (1/2+1)(1/3+1)(1/4+1)...(1/2017+1)(1/2018 +1)`
`C= 3/2. 4/3 .5/4 .... 2018/2017 . 2019/2018`
`C= (3.4.5...2018.2019)/(2.3.4....2017.2018)`
`C= 2019/2. (3.4.5....2017.2018)/(3.4.5....2017.2018)`
`C= 2019/2 vì (3.4.5....2017.2018)/(3.4.5....2017.2018)= 1`