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¨§ËÒ¤èҢͧ $$1-\frac{2}{4}+\frac{2\times5}{4\times8}-\frac{2\times5\times8}{4\times8\times12}+.....$$ ã¤ÃÁÕ¤Óàà¹Ð¹Ó ªèÇÂ˹èͤÃѺ :please: :please:
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´Ñ§¹Ñé¹ $(1-x)^n = 1 - nx + \frac{n(n-1)}{2!}x^2 - \frac{n(n-1)(n-2)}{3!}x^3+...$ |
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$$1-\frac{2}{4}+\frac{2\times5}{4\times8}-\frac{2\times5\times8}{4\times8\times12}+...=1-nx+\frac{n(n-1)}{2!}x^2-...$$ à·ÕºÊÑÁ»ÃÐÊÔ·¸Ôì $nx=\frac{2}{4}$--------(1) $\frac{n(n-1)}{2!}x^2=\frac{2\times5}{4\times8}$-------(2) á¡éËÒ¤èÒ $n$ áÅÐ $x$ áÅéÇá·¹¤èÒ ·ÕèËÒä´éã¹ $(1-x)^n$ ¤ÃѺ |
#5 ¾Õègon ¤ÃѺ
áÅÐàÁ×èͤԴµèͨÐä´é¤èÒ $n=\frac{-2}{3}$ , $x= \frac{-3}{4}$ á·¹¤èÒ¡é¨Ðä´é $\sqrt[3]{\frac{16}{49}}$ |
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àÇÅÒ·ÕèáÊ´§·Ñé§ËÁ´ à»ç¹àÇÅÒ·Õè»ÃÐà·Èä·Â (GMT +7) ¢³Ð¹Õéà»ç¹àÇÅÒ 10:20 |
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