1-1/2 +1/2-1/3+1/3-1/4+…1/2008-1/2009
=1+(-1/2+1/2)+(-1/3+1/3)+(-1/4+1/4)+.+(-1/2008+1/2008)-1/2009
=1+0+0+0+...+0-1/2009
=1-1/2009
=2008/2009
1-1/2 +1/2-1/3+1/3-1/4+…1/2008-1/2009
=1+(-1/2+1/2)+(-1/3+1/3)+(-1/4+1/4)+.+(-1/2008+1/2008)-1/2009
=1+0+0+0+...+0-1/2009
=1-1/2009
=2008/2009