原式=1/11-1/12+1/12-1/13+1/13-1/14=1/11-1/14=3/154
原式等于1/11-1/12+1/12-1/13+1/13-1/14=1/11-1/14=3/154
=1/11-1/12+1/12-1/13+1/13-1/14=1/11-1/14=3/154