1:
a: 2018/2017>1
2012/2013<1
=>2018/2017>2012/2013
b: 57/56=1+1/56
38/37=1+1/37
mà 1/56<1/37
nên 57/56<38/37
c: 2016/2017=1-1/2017
2018/2019=1-1/2019
mà 1/2017>1/2019
nên 2016/2017<2018/2019
e: \(\dfrac{456}{461}=1-\dfrac{5}{461}\)
123/128=1-5/128
mà 5/461<5/128
nên 456/461>123/128
f: \(A=1-\dfrac{1}{2007\cdot2008}\)
B=1-1/2008*2009
2007*2008<2008*2009
=>1/2007*2008>1/2008*2009
=>A<B