Đáp án:
`A=27/28`
`B=0`
Giải thích các bước giải:
`A=6/8+6/56+6/140+...+6/1100+6/1400`
`=3/4+3/28+3/70+...+3/550+3/700`
`=3/1.4+3/4.7+3/7.10+...+3/22.25+3/25.28`
`=1-1/4+1/4-1/7+1/7-1/10+...+1/22-1/25+1/25-1/28`
`=1-1/28`
`=27/28`
$\\$
`B=(1-1000/2016).(1-1001/2016).(1-1002/2016).….(1-2017/2016)`
`=(1-1000/2016).(1-1001/2016).(1-1002/2016)...(1-2016/2016).(1-2017/2016)`
`=(1-1000/2016).(1-1001/2016).(1-1002/2016)...(1-1).(1-2017/2016)`
`=(1-1000/2016).(1-1001/2016).(1-1002/2016)...0.(1-2017/2016)`
`=0`