（-1/42)除以（1/6-3/14+2/3-2/7）=-1÷（42×1/6-42×3/14+42×2/3-42×2/7）=-1÷（7-9+28-12）=-1÷14=-1/141又3分之一-7/12+9/20-11/30+13/42-15/56+17/72=1+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...