#16
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¼ÅµèÒ§¡ÓÅѧÊͧ áÅСÓÅѧÊͧÊÁºÙóì ÁѹÍÂÙèã¹á¿¤àµÍÃì¹èÐ àÍè͹Ñè¹ÊÔ »ÃжÒÁ»ÅÒÂàÃÕ¹áÅéÇËÃͤÐ??
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5555 09 ÁԶعÒ¹ 2008 19:24 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ mathematiiez |
#17
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ÂѧÍèÐ áµèàÃÕ¹¾ÔàÈÉáÅéÇ
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16 ÁԶعÒ¹ 2008 21:13 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ ¤usÑ¡¤³Ôm |
#18
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ÍëÍ àÃÕ¹Åèǧ˹éÒ¡ç´ÕàËÁ×͹¡Ñ¹áÎÐ ^^
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#19
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1+4+7..........n
=$\frac{1+n}{2}[(\frac{n-1}{3})+1]$
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04 ÊÔ§ËÒ¤Á 2008 21:07 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ ¤usÑ¡¤³Ôm |
#20
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ÊٵüźǡàÅ¢¤Õè¤×Í [ (n+1) /2 ]2 n=µÑÇ·éÒÂ
14 ¡Ñ¹ÂÒ¹ 2008 17:18 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ jewjew |
#21
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µ¡Å§¹ÕèÁѹËéͧ¤³ÔµÈÒʵÃì»ÃжÁ»ÅÒÂËÃ×Íà»ÅèҤѺ(¼Á¡çäÁèäªè»ÃжÁ»ÅÒÂáËÐæ)
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¤¹àÃÒËÒ¡ÅéÁ¡çµéͧÅØ¡ ¼Ùéã´ÅéÁààÅéÇäÁèÅØ¡¼Ùé¹Ñé¹ÂÔ觡ÇèÒÊعѢ ÊعѢÁѹÅéÁààÅéÇÁѹÂѧÅØ¡ä´é ààÅéÇ·ÓäÁ¤¹¶Ö§¨ÐÅØ¡äÁèä´é |
#22
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sigma i = n(n+1)/2
sigma i2 = n(n+1)(2n+1)/6 sigma i3 = [n(n+1)/2]2 |
#23
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[quote=¤usÑ¡¤³Ôm;28509]ÁÕÍÕ¡ a(¡¡ÓÅѧÊͧ)+b(¡¡ÓÅѧÊͧ) ¨Ðà·èҡѺ (a+b)¤Ù³(a-b)àÊÁÍæ
¼Ô´ËÃ×Í»èÒǤѺ $a^2+b^2\not= (a+b)(a-b)$¤Ñº ààµè¶éÒ$a^2-b^2=(a+b)(a-b)$¤Ñº
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¤¹àÃÒËÒ¡ÅéÁ¡çµéͧÅØ¡ ¼Ùéã´ÅéÁààÅéÇäÁèÅØ¡¼Ùé¹Ñé¹ÂÔ觡ÇèÒÊعѢ ÊعѢÁѹÅéÁààÅéÇÁѹÂѧÅØ¡ä´é ààÅéÇ·ÓäÁ¤¹¶Ö§¨ÐÅØ¡äÁèä´é |
#24
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ÍéÒ§ÍÔ§:
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#25
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äÁèä´éËŧËÃÍ¡¤ÃѺ ÁѹÂѧÁÕà˵ءÒ÷Õèà»ç¹¨ÃÔ§¤×Í b= 0 ËØËØ
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#26
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#27
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#28
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ËÅÑ¡¢Í§¡ÒÃà¢Õ¹ÅӴѺ¤×ÍàÃÒµéͧà¢Õ¹¾¨¹ì·Õè n à¹ÕèÂà»ç¹¾¨¹ì·ÑèÇ仹ФÃѺ àªè¹
ÅӴѺ 1+4+7+... ¾¨¹ì·ÑèÇ令×Í 1+(n-1)(3) = 3n-2 ¤ÃѺ à¢Õ¹à»ç¹ÅӴѺãËÁèä´éÇèÒ $S_n = 1+4+7+...+(3n-2)$ $S_n = (3n-2)+(3n-5)+(3n-8)+...+1$ $2S_n = (3n-1)+(3n-1)+(3n-1)+...+(3n-1)$ $2S_n = (3n-1)(n)$ $S_n = \frac{(3n-1)(n)}{2}$ àÁ×èÍ n ¤×ͨӹǹ¾¨¹ì¢Í§ÅӴѺ ãËé N ¤×;¨¹ìÊØ´·éÒ¢ͧÅӴѺ¨Ðä´éÇèÒ $\frac{N+2}{3} = n$ ¨Ðä´é $S_n = \frac{(N+1)(N+2)}{6}$ àÁ×èÍ N ¤×;¨¹ìÊØ´·éÒ¢ͧÅӴѺ¤ÃѺ 14 µØÅÒ¤Á 2008 17:13 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 2 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ [SIL] |
#29
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????
ÊٵþËعÒÁËÃÍ ¤ÃѺ |
#30
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Íѹ¹Õéà¢Ò¶Ö§àÃÕ¡ÇèÒ ¾ËعÒÁ
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15 µØÅÒ¤Á 2008 19:44 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 2 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ ¤usÑ¡¤³Ôm |
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