|1/2009-1/2008|+|1/2008-1/2007|+|1/2007-1/2006|
=1/2008-1/2009+1/2007-1/2008+1/2006-1/2007
=1/2006-1/2009
=(2009-2006)/2009*2006
=3/4030054
如果一直加到|1/2-1|
|1/2009-1/2008|+|1/2008-1/2007|+|1/2007-1/2006|`````+|1/3-1/2|+|1/2-1|
=(1/2008-1/2009)+(1/2007-1/2008)+(1/2006-1/2007)+...+(1/2-1/3)+(1-1/2)
=1-1/2009
=2008/2009