解
丨1/2008-1/2009丨+丨1/2009-1/2010丨+丨1/2010-1/2011丨
=(1/2008-1/2009)+(1/2009-1/2010)+(1/2010-1/2011)
=1/2008+(1/2009-1/2009)+(1/2010-1/2010)-1/2011
=1/2008-1/2011
=3/4038088