问个不容易回答的，

这个题目的标准答案是什么？狗不到，只能求人,

For series S_n=Sum(n!x^n), what value of x will make the series converge?

所有跟帖： 

• 绝对值小于 -又当爹来又当妈- ♀ (567 bytes) () 09/30/2016 postreply 09:01:22

• x=0 only -BeLe- ♀ (107 bytes) () 09/30/2016 postreply 09:02:24

• 多谢，儿子说是0。我以为还有别的值，比如1/2(n+1) -flagsix- ♂ (0 bytes) () 09/30/2016 postreply 09:22:37

• x is a fixed value, so it is independent of n. -BeLe- ♀ (0 bytes) () 09/30/2016 postreply 09:25:55

• 再次感谢。这些东西早都忘了。也许当年也没搞明白, 不是数理专业的 -flagsix- ♂ (0 bytes) () 09/30/2016 postreply 09:41:24

• 和收敛的条件是项要趋于零，所以必须n!x^n的极限为零才行。而X如果是常数不行，设X=1/M -嘚瑟一下- ♂ (47 bytes) () 09/30/2016 postreply 09:17:25

• 必要，不充分 -又当爹来又当妈- ♀ (113 bytes) () 09/30/2016 postreply 09:32:40

• 楼主的题除了X=0,其它数都没满足必要条例 -嘚瑟一下- ♂ (0 bytes) () 09/30/2016 postreply 09:35:10

• x=0 -welovegod- ♂ (143 bytes) () 09/30/2016 postreply 09:47:26

• perfect! -wujiandao- ♀ (0 bytes) () 09/30/2016 postreply 10:22:52