把所有分数都拆开来5/6=1/2+1/37/12=1/3+1/49/20=1/4+1/511/30=1/5+1/613/42=1/6+1/715/56=1/7+1/817/72=1/8+1/9然后代入原式得：原式=-1+(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)+(1/8+1/9)=-...