1x1⼀3+3x1⼀5+5x1⼀7+2n减一乘以2n加1⼀1的解法。

数学计算题。
2025-03-15 20:18:29
推荐回答(1个)
回答1:

an
= 1/[(2n-1)(2n+1)]
= (1/2) [ 1/(2n-1)-1/(2n+1) ]
Sn
=a1+a2+...+an
= (1/2) [ 1-1/(2n+1) ]
=n/(2n+1)