#1
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͹ءÃÁ͹ѹµì2
$$\sum_{n=1}^\infty \frac{5n^2+5n-3 \cdot2^n}{2^n\cdot n^2+2^n}$$
ËÒä´éÍÂèÒ§ääÃѺ
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âÅ¡¹ÕéÁÕ¤¹ÍÂÙè 10 »ÃÐàÀ· ¤×Í ¤¹·Õèà¢éÒã¨àÅ¢°Ò¹Êͧ áÅФ¹·ÕèäÁèà¢éÒ㨠15 ¾ÄȨԡÒ¹ 2006 17:34 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 3 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ Mastermander |
#2
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àÍÒ⨷ÂìÁÒ¨Ò¡ä˹¤ÃѺà¹Õè random ¢Öé¹ÁÒàͧÃÖà»ÅèÒ ´Ù¤ÃèÒÇæáÅéÇäÁè¹èÒËҤӵͺÍÍ¡ÁÒã¹ÃÙ»»Ô´ä´é áµè¶éÒà»ç¹ numerical value áÅéÇËÒä´é§èÒÂÁÒ¡¤ÃѺ ¼ÁËÒä´éà·èҡѺ
2.2432733791927400348854352209819334941715... |
#3
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¨ÃÔ§æáÅéǨеÑé§â¨·Âìà»ç¹
$$ \sum_{n=1}^\infty \frac{5n^2+5n-3\cdot 2^n}{2^n\cdot n^2+2^n\cdot n} $$ áµèºÑ§àÍÔ¾ÔÁ¾ì n µ¡ä»µÑǹ֧ áÅéÇâ¾Êµì⨷Âì¹Õéŧä»áÅéÇ...¡çàÅÂÁÒËҤӵͺ·Õè¹Õè¤ÃѺ ¢Íº¤Ø³ÁÒ¡¤ÃѺ ¶éÒ·èÒ¹ã´ÁÕÇÔ¸Õ¤Ô´µÃ§æ¡çºÍ¡¡ÅèÒǡѹ´éǹФÃѺ
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#4
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ÍëÍ... ¶éÒà»ç¹Íѹ¹Õé¡ç§èÒÂÁÒ¡¤ÃѺ
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#5
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ᡵÑÇ»ÃСͺ·Ñ駵ÑÇàÈÉáÅеÑÇÊèǹ áÅéÇá¡à·ÍÁ¨Ðä´é
$$\sum_{n=1}^\infty \frac{5n^2+5n-3\cdot 2^n}{2^n\cdot n^2+2^n\cdot n} =5\sum_{n=1}^\infty\frac{1}{2^n}-3\sum_{n=1}^\infty\frac{1}{n(n+1)}=5-3=2$$
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¤¹ä·ÂÃèÇÁã¨ÍÂèÒãªéÀÒÉÒÇÔºÑµÔ ½Ö¡¾ÔÁ¾ìÊÑÅѡɳìÊÑ¡¹Ô´ ªÕÇÔµ(¤¹µÍºáÅФ¹¶ÒÁ)¨Ð§èÒ¢Öé¹àÂÍÐ (¨ÃÔ§æ¹Ð) Stay Hungry. Stay Foolish. |
#6
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âÅ¡¹ÕéÁÕ¤¹ÍÂÙè 10 »ÃÐàÀ· ¤×Í ¤¹·Õèà¢éÒã¨àÅ¢°Ò¹Êͧ áÅФ¹·ÕèäÁèà¢éÒ㨠|
#7
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259. (ËҡʧÊÑÂÅͧ令鹴ÙàÃ×èͧ power series ´Ù¹Ð¤ÃѺ)
$$\begin{eqnarray} x+\frac{5x^3}{2\cdot3}+\frac{9x^5}{4\cdot5}+\frac{13x^7}{6\cdot7}+\ldots &=&x+(\frac{1}{2}+\frac{1}{3})x^3+(\frac{1}{4}+\frac{1}{5})x^5+(\frac{1}{6}+\frac{1}{7})x^7+\ldots\\ &=&(x+\frac{x^3}{3}+\frac{x^5}{5}+\ldots)+\frac{x}{2}(x^2+\frac{x^4}{2}+\frac{x^6}{3}+\ldots)\\ &=&\text{arctanh}\; x-\frac{x}{2}\ln{(1-x^2)}\\ \end{eqnarray}$$ 260. ¨Ò¡ $$(1-x)^{-2/3}=1+\frac{2}{3}x+\frac{2\cdot5}{3\cdot6}x^2 +\frac{2\cdot5\cdot8}{3\cdot6\cdot9}x^3+\ldots$$ àÁ×èÍãËé x=1/2 ¨Ðä´é¼ÅÃÇÁ͹ءÃÁ·Õèµéͧ¡Òä×Í $2^{2/3}$
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¤¹ä·ÂÃèÇÁã¨ÍÂèÒãªéÀÒÉÒÇÔºÑµÔ ½Ö¡¾ÔÁ¾ìÊÑÅѡɳìÊÑ¡¹Ô´ ªÕÇÔµ(¤¹µÍºáÅФ¹¶ÒÁ)¨Ð§èÒ¢Öé¹àÂÍÐ (¨ÃÔ§æ¹Ð) Stay Hungry. Stay Foolish. |
#8
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¢Íº¤Ø³ÁÒ¡¤ÃѺ
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âÅ¡¹ÕéÁÕ¤¹ÍÂÙè 10 »ÃÐàÀ· ¤×Í ¤¹·Õèà¢éÒã¨àÅ¢°Ò¹Êͧ áÅФ¹·ÕèäÁèà¢éÒ㨠13 àÁÉÒ¹ 2006 11:48 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ Mastermander |
#9
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$$\int x\, d(\ln|1-x^2|) =\int \frac{2x^2}{x^2-1} \,dx$$ $$= \int2+ \frac{1}{x-1}- \frac{1}{x+1} \,dx$$ $$=2x+ \ln|x-1|- \ln|x+1| +C$$ $$=2x +\ln \left| \frac{x-1}{x+1} \right| +C$$ $$=2x+ \ln \left| \frac{1-x}{1+x} \right| +C$$
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#10
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¨Ò¡ÃÙ»·Õè¼ÁṺäÇé´éÒ¹º¹ ºÃ÷Ѵ·Õè 2 ¹Ñº¨Ò¡´éÒ¹ ÅèÒ§ µéͧÁÕÍÍ¡ÁÒà»ç¹ -x à¾×èÍãËé¼ÅÅѾ¸ìà»ç¹ºÃ÷ѴÊØ´·éÒÂ
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#11
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$ \because \, c=-1 \ne1$
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#12
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¢Í¶ÒÁÇèÒ·ÓäÁ ¤èÒ¤§·Õèà»ç¹ -1 ¤ÃѺ
ã¹àÁ×èÍ¡è͹´Ô¿àÃÒ·ÃÒºÇèÒ ¤èÒ¤§·Õè¤×Í 1 áÅéÇ ·ÓäÁ¾ÍÍÔ¹·Ôà¡Ãµ¡ÅѺ äÁèä´é¤èÒ¤§·ÕèµÑÇà´ÔÁËÃͤÃѺ
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#13
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¨Ò¡·Õè $$\left. \frac{ds}{dx} \right|_{x=0} =1$$ ´Ñ§¹Ñé¹àÁ×èÍ $x=0$ àÃҨеéͧä´éÇèÒ $$ -\frac12 \ln |1-x^2|+ 2(1-x^2)^{-1} +c=1$$ á¡éÊÁ¡ÒÃáÅéÇàÃҨоºÇèÒ $c=-1$ ¤ÃѺ
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#14
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¨§ËҼźǡ͹ءÃÁ¨¹¶Ö§ n à·ÍÁ
12 + 123 + 1234 + 12345 + ...
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#15
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¶éÒËÒ¶Ö§à·ÍÁ·Õè n Áѹà»ç¹ä»ä´éËÅÒÂẺ¹Ð¤ÃѺ àªè¹
...+123456789+1234567890+12345678901+123456789012+... ...+123456789+12345678910+1234567891011+123456789101112+... ...+123456789+1234567891+12345678912+123456789123+1234567891234+... ÏÅÏ ¨ÐàÍÒÂѧä§ÅͧºÍ¡ÁÒãËéªÑ´ÍÕ¡·Õ¹Ð¤ÃѺ
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¤¹ä·ÂÃèÇÁã¨ÍÂèÒãªéÀÒÉÒÇÔºÑµÔ ½Ö¡¾ÔÁ¾ìÊÑÅѡɳìÊÑ¡¹Ô´ ªÕÇÔµ(¤¹µÍºáÅФ¹¶ÒÁ)¨Ð§èÒ¢Öé¹àÂÍÐ (¨ÃÔ§æ¹Ð) Stay Hungry. Stay Foolish. |
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