Đáp án:
Bài 5:
Ta có:
`(2015 + 2016 + 2017)/(2016 + 2017 + 2018)`
`= 2015/(2016 + 2017 + 2018) + 2016/(2016 + 2017 + 2018) + 2017/(2016 + 2017 + 2018)`
Mà `2015/(2016 + 2017 + 2018) < 2015/2016`
`2016/(2016 + 2017 + 2018) < 2016/2017`
`2017/(2016 + 2017 + 2018) < 2017/2018`
`⇒ 2015/(2016 + 2017 + 2018) + 2016/(2016 + 2017 + 2018) + 2017/(2016 + 2017 + 2018) < 2015/2016 + 2016/2017 + 2017/2018`
Hay `A > B`