求助一道数学题:1-1⼀2+1⼀3-1⼀4+1⼀5-1⼀6+1⼀7-1⼀8+1⼀9……+1⼀19-1⼀20=?

2024-12-18 02:41:28
推荐回答(3个)
回答1:

1-1/2+1/3-1/4+...+1/19-1/20=(1-1/2+1/3-1/4+1/5-1/6+1/7-1/8+1/9-1/10)-(1/12+1/14+1/16+1/18+1/20)+(1/11+1/13+1/15+1/17+1/19)=1/11+(1/3-1/6-1/12)+1/13+(1/7-1/14)+1/15+(1-1/2-1/4-1/8-1/16)+1/17+(1/9-1/18)+1/19+(1/5-1/10-1/20)=1/11+1/12+...+1/20=155685007/232792560

回答2:

1/11+1/12+...+1/20=155685007/232792560

回答3:

155685007/232792560