原式=1+1/2-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7+5=6
3/2-5/6+7/12-9/20+11/30-13/42+15/56
=9/6-5/6+7/12-9/20+11/30-13/42+15/56
=4/6+7/12-9/20+11/30-13/42+15/56
=8/12+7/12-9/20+11/30-13/42+15/56
=15/12-9/20+11/30-13/42+15/56
=5/4-9/20+11/30-13/42+15/56
=25/20-9/20+11/30-13/42+15/56
=16/20+11/30-13/42+15/56
=4/5+11/30-13/42+15/56
=24/30+11/30-13/42+15/56
=35/30-13/42+15/56
=7/6-13/42+15/56
=49/42-13/42+15/56
=36/42+15/56
=6/7+15/56
=48/56+15/56
=63/56
=9/8