1/1×3+1/3×5+1/5×7+1/7×9+1/9×11+......1/49×51=1/2×(1-1/3)+1/2×(1/3-1/5)+1/2×(1/5-1/7)+....+1/2×(1/49-1/51)=1/2×(1-1/3+1/3-1/5+1/5-1/7+...+1/49-1/51)=1/2×(1-1/51)=1/2×50/51=25/51;有帮助记得好评，新问题请重新发帖提问，这里不再回答谢谢
