inequalities

2012-04-21 2:08 am
Prove
n + 1 + 1/2 + 1/3 + . . . + 1/n > n(n + 1)^(1/n)
更新1:

for integer n>1

回答 (3)

2012-04-21 5:10 am
✔ 最佳答案
n + 1 + 1/2 + 1/3 + . . . + 1/n

= (1 + 1) + (1 + 1/2) + (1 + 1/3) + ... + (1 + 1/n)

= 2 + 3/2 + 4/3 + ,,, + (n + 1)/n

> n [2 * 3/2 * 4/3 * ... * (n + 1)/n]^(1/n)

because A.S. > G.S. as 2, 3/2,... (n + 1)/n are not equal

= n(n + 1)^(1/n)
2012-04-21 2:20 am
what's the domain of n?
2012-04-21 2:15 am
P(n) : n + 1 + 1/2 + 1/3 + . . . + 1/n > n(n + 1)^(1/n)
其中 n 為正整數

當 n = 1 :
左式 = 1 + 1 = 2
右式 = 1(1 + 1)^(1/1) = 2
左式 = 右式

故命題 P(n) 不成立。


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