a=(2006-1)(2006+1)/2006
=2006-1/2006
b=(2007-1)(2007+1)/2007
=2007-1/2007
c=(2008-1)(2008+1)/2008
=2008-1/2008
∵1/2006 1/2007 1/2008都是小于1的
∴a
a=(2006-1)(2006+1)/2006
=2006-1/2006
b=(2007-1)(2007+1)/2007
=2007-1/2007
c=(2008-1)(2008+1)/2008
=2008-1/2008
∵1/2006 1/2007 1/2008都是小于1的
∴a