推 n19860423 :先取log 05/19 00:32
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→ penny93730 :樓上真是出乎意料...好我再算...晚安～ 05/19 00:33
→ n19860423 :我PO一下好了~"~ 05/19 00:33
(1+x)(2+x)(3+x)......(9+x)
f(x)= ----------------------------
(1-x)(2-x)(3-x)......(9-x)
求f'(0)
9
Ans: 2 Σ (1/n)
n=1
感謝回答:)
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