Simone
2008x2010/2009+2009x2011/2010+4019/（2009X2010)
=(2009-1)(2009+1)/2009+(2010-1)(2010+1)/2010+1/2009+1/2010
=(2009^2-1)/2009+(2010^2-1)/2010+1/2009+1/2010
=2009^2/2009-1/2009+2010^2/2010-1/2010+1/2009+1/2010
=2009-1/2009+2010-1/2010+1/2009+1/2010
=2009+2010
=4019
