(-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+……+1/2008-1/2009]=-[1-1/2009]=-2008/2009 .
负2009分之2008
-2008分之2009