A=2009.2011 và B=\(2010^2\)
Ta có: A=2009.(2010+1)
A=2009.2010+2009
B=\(2010^2\) =2010.2010=(2009+1).2010
B=2009.2010+2010
Mà 2010>2009 nên A<B
\(A=2009\left(2009+2\right)=2009^2+2.2009\)
\(B=\left(2009+1\right)^2=2009^2+2.2009+1\)
=>A<B
A = 2009 . 2011
A = 2009 . (2010 + 1)
A = (2009 + 1) . 2010
Mà B = 20102 = 2010 . 2010
Vậy A = B