Question

高中数学，数列有一点没看懂

bn=1/n,
Sn=1+1/2+......+1/n
所以，Tn=S2n-Sn=1/(n+1)+1/(n+2)+1/(n+3)+......+1/2n(这里没看懂，怎么得来？）
Tn+1=1/(n+2)+1/(n+3)+......+1/2n+1/(2n+1)+1/(2n+2)
所以；Tn+1-Tn=1/(2n+1)+1/(2n+2)-1/(n+1)（哦，这里看懂了，刚看懂。就说上面的吧）谢谢
S2n=?

Answer 1

Tn=S2n-Sn=1/(n+1)+1/(n+2)+1/(n+3)+......+1/2n
就是把n值用2n代人
S2n=1+1/2+......+1/n+……+1/2n
减掉Sn就只剩后面的了。

Answer 2

S2n=1+1/2+1/3+...+1/n+1/(n+1)+1/(n+2)+...+1/(2n)
Sn=1+1/2+......+1/n
令Tn=S2n-Sn
则Tn=1/(n+1)+1/(n+2)+1/(n+3)+......+1/2n（哪里不明白）
T(n+1)=S(2n+2)-S(n+1)

Answer 3

S2n=1+1/2+1/3+...+1/n+1/(n+1)+1/(n+2)+...+1/(2n)
Sn=1+1/2+......+1/n
令Tn=S2n-Sn
则Tn=1/(n+1)+1/(n+2)+1/(n+3)+......+1/2n
T(n+1)=S(2n+2)-S(n+1)