一問一答問題 -1/10乗11-1/11乗12-1/12乗13-1/19乗20 -1/2-1/6-1/12-1/20-1/30-1/42

一問一答問題 -1/10乗11-1/11乗12-1/12乗13-1/19乗20 -1/2-1/6-1/12-1/20-1/30-1/42

-1/10乗11-1/11乗12-1/12乗13.-1/19乗20=-(1/10-1/11+1/11-1/12+.+1/19-1/20)=-1/1/2-1/2-1/2-1/6-1/12-1/20-1/30-1/22=-(1-1/2+1/2-1/3+1/3-1/4+...+1/6-1/7)=-(1-1/7)=-6/7