急! 1題 limit, 要show work

2009-10-09 11:35 pm
lim (x * logx)
x-> 0+
更新1:

點解 [1/ln(10)] lim [x->0+] ln(x) / (1/x) = [1/ln(10)] lim [x->0+] (1/x) / -(1/x^2)

回答 (1)

2009-10-09 11:51 pm
✔ 最佳答案

log(x) = ln(x) / ln(10)
lim [x->0+] xlog(x)
= lim [x->0+] xln(x) / ln(10)
= [1/ln(10)] lim [x->0+] ln(x) / (1/x)
= [1/ln(10)] lim [x->0+] (1/x) / -(1/x^2)
= [1/ln(10)] lim [x->0+] (-x)
= 0

2009-10-09 16:49:57 補充:
可參考http://en.wikipedia.org/wiki/L'H%C3%B4pital's_rule
l'Hôpital's rule


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