Đáp án:
B=(2010+2011)/(2011+2012) =2010/(2011+2012) +2011/(2011+2012)
ta có 2010/2011 > 2010/(2011+2012)
và 2011/2012>2011/(2011+2012)
suy ra 2010/2011 +2011/2012 >2010/(2011+2012) +2011/(2011+2012)
hay 2010/2011 +2011/2012 >(2010+2011)/(2011+2012)
vậy A>B