ab+2=0 , a+1=0所以 a=-1, b=2所以原式等于-1/(2x3)-1/(3x4)-1/(4x5)...-1/(2005x2006)负号提出来可得-[1/(2x3)+1/(3x4)+1/(4x5)...+1/(2005x2006)]括号里面的裂项就可以即1/(2x3)=1/2-1/31/(3x4)=1/3-1/4...如此类...