|1/2009-1/2008|+|1/2008-1/2007|+|1/2007-1/2006|+...+|1/3-1/2|+|1/2-1|
=-(1/2009-1/2008)-(1/2008-1/2007)-(1/2007-1/2006)-...-(1/3-1/2)-(1/2-1)
=-[(1/2009-1/2008)+(1/2008-1/2007)+(1/2007-1/2006)+...+(1/3-1/2)+(1/2-1)]
=-[1/2009-1]
=2008/2009