A = 2009.2011 = (2010-1)(2010 + 1) = 20102 - 12 = 20102 - 1
B = 2010 . 2010 = 20102
Do 20102 - 1 < 20102
< = > A < B
ta có : 2009.2011=(2009+1).(2011-1)==>>> 2010.2010===>>> 2010.2010=2010.2010=>> 2009.2011=2010.2010
A = 2009 . 2011
= 2009 . (2010 + 1)
= 2009 . 2010 + 2009 . 1
B = 2010 . 2010
= 2010 . (2009 + 1)
= 2010 . 2009 + 2010 . 1
Vì 2009 . 2010 = 2010 . 2009 và 2009 . 1 < 2010 . 1
=> 2009 . 2010 + 2009 . 1 < 2010 . 2009 + 2010 . 1
=> A < B.
Ta có:A=2009.2011=2009.(2010+1)=2009.2010+2009
B=2010.2010=(2009+1).2010=2009.2010+2010
Vì 2009<2010 nên A<B
tick nha