b－1的相反数等于它本身,b-1=-(b-1),解得b=1
ab与－2互为相反数,ab-2=0,解得a=2.
ab分之1＋（a+1)(b+1)分之1＋.＋（a+2006)(b＋2006)
=1/1*2+1/2*3+.+1/2007*2008
=1-1/2+1/2-1/3+...+1/2007-1/2008
=1-1/2008
=2007/2008