( 2015 +2016.2017)/( 2017.2018 -2019)
Tử số: 2015 +2016.2017= 2017.(2017-1) +2015
= 2017.2017 -2017 +2015
= 2017.2017 -2
Mẫu số: 2017.2018 -2019= 2017.(2017 +1) -2019
= 2017.2017 -2019
= 2017.2017 -2
⇒ (2017.2017 -2)/(2017.2017 -2) = 1
⇒ ( 2015 +2016.2017)/( 2017.2018 -2019) = 1
Chúc bạn học tốt ^^