原式=1.5-3+1/6+3+1/12-5+1/20+5+1/30-7+1/42+7+1/56-9+1/72+9+1/90 =1.5+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90 =1.5+1/4+1/20+1/30+1/42+1/56+1/72+1/90 =1.5+3/10+1/30+1/42+1/56+1/72+1/90 =1.5+1/3+1/42+1/56+1
