(2+4+6…+2006+2008)-(1+3+5+…+2005+2007)=
=2+4+6…+2006+2008-1-3-5-…-2005-2007
=2-1+4-3+6-5+……+2008-2007
=1+1+1+……+1
=1×1004
=1004