由已知得（a-1）的算术平方根=0（ab-2）^2=0即a=1,b=21/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+…+1/(a+2004)(b+2004)=1/1*2+1/2*3+1/3*4)+…+1/2005*2006=(1-1/2)+(1/2-1/3)+(1/3-1/4))+…+(1/2005-1/2006)=1-1/2006=2005/2...