知lab-2l与llb-1l互为相反数，ab-2=0b-1=0 所以 b=1 a=2ab分之一+1/(a+1)(b+1)+1/(a+2)(b+2)+···+1/(a+2009)(b+2009)=1/1*2+1/2*3+1/3*4+……+1/2010*2011=1-1/2+1/2-1/3+1/3-1/4+……+1/2010-1/2011=1-1/2011=2010/2011
