#1
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Cardan's Method
¡ÒÃËÒÃÒ¡¢Í§¾ËعÒÁ¡ÓÅѧÊÒÁÍèФÃѺ¤×ÍÇèÒ¼ÁÅͧÍèÒ¹´ÙáÅéÇÍèФÃѺ Áѹ§§æ¹Ô´¹Ö§
¾ÍàÃҨѴÃÙ»ÊÁ¡Òèҡ $ax^{3} + bx^{2} + cx + d$ãËéà»ç¹ $t^{3} + pt +q$ áÅéÇËÅѧ¨Ò¡¹Ñé¹ ãËé $t = u+v$ à»ç¹ÃÒ¡¢Í§ÊÁ¡Òà $t^{3} + pt +q$ ¹Ñ鹤×ÍÊÁÁµÔÃÒ¡ÍÂÙèã¹ÃٻẺ u+v áÅéǨÐËÒ u áÅÐ v«Ö觨Ðä´é $u^{3} +v^{3} + (3uv + p)(u + v) = o$ (µèͨҡ¹Õé¤×ͨش·Õ觧¤ÃѺ) à¾×èÍãËéäÁèÁÕ¡ÓÅѧ˹Ö觨֧ãËé $3uv + p = 0$ áÅШÐä´é $u^{3} + v^{3} = -q$ ·ÓãËéä´éÃкºÊÁ¡Òà $u^{3} +v^{3} =-q$ áÅÐ $uv = -\frac{p}{3}$ (áÅéÇàÃÒ¡ÓËÁ´ãËéäÁèÁÕ¡ÓÅѧ˹Öè§ä´éàËÃͤÃѺ) «Öè§áÊ´§ÇèÒ $u^{3} + v^{3}$ à»ç¹ÃÒ¡¢Í§ÊÁ¡Òà $y^{2} + qy - \frac{p^{3}}{27} = 0$ (ÃÙéä´é䧤ÃѺÇèÒÁѹ¨Ðà»ç¹ÃÒ¡¢Í§ÊÁ¡ÒùÕé) ¾Íä´é¶Ö§¢Ñé¹¹ÕéáÅéÇ·ÓÂѧ䧵èÍàËÃͤÃѺ$ edit¶ÒÁà¾ÔèÁ¤ÃѺ áÅéǼÅà©Å¢ͧ congruet ÊÒÁÒö¹Óä»·ÓÍÐäÃä´éºéÒ§¤ÃѺ áÅéÇ¡ç Congruet,modulo»ÃÐÂØ¡µìãªéã¹ ¡ÒÃá¡é⨷Âì»ÑËÒµèÒ§æä´éÂѧä§àËÃͤÃѺ ¾Í´ÕÍèÒ¹à¹×éÍËÒÂèÍæáÅéÇáµèäÁèÃÙé¨Ð»ÃÐÂØ¡µìãªéã¹â¨·Âì»ÃÐàÀ·ä˹ ÍÂèÒ§äà ¶éÒÁÕàÇÅÒ¡ç¡ÃسҪèÇ¡µÑÇÍÂèҧ⨷ÂìÊÒÁÒöãªécongruetá¡éä´éÍèФÃѺ
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..................ʹء´Õà¹ÍÐ................... 22 ¸Ñ¹ÇÒ¤Á 2006 17:03 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 5 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ CmKaN |
#2
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¶ÒÁµèÍàŹФÃѺ $x^{3} - 3x^{2} - 3x -1 =0$
ÁÕÃÒ¡¢Í§ÃкºÊÁ¡Òà à»ç¹ÍÂèÒ§¹ÕéäËÁ¤ÃѺ $\sqrt[3]{\frac{7 + \sqrt{ 17 }}{2} }$ + $\sqrt[3]{ \frac{7 - \sqrt{ 17 }}{2} }$ + $1$ , $\sqrt[3]{\frac{7 + \sqrt{ 17 }}{2} }$w + $\sqrt[3]{ \frac{7 - \sqrt{ 17 }}{2} }\omega^{2}$ + $1$ , $\sqrt[3]{\frac{7 + \sqrt{ 17 }}{2} }\omega^{2}$ + $\sqrt[3]{ \frac{7 - \sqrt{ 17 }}{2} }\omega$ + $1$ àÁ×èÍ $\omega$ à»ç¹ÃÒ¡»°Á°Ò¹ $\omega^{2}$
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..................ʹء´Õà¹ÍÐ................... 22 ¸Ñ¹ÇÒ¤Á 2006 13:54 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ CmKaN |
#3
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¼ÁàÅ×Í¡µÍº¤Ó¶ÒÁ·Õè͸ԺÒ§èÒ¡è͹¹Ð¤ÃѺ.
µÃ§¨Ø´áá·Õèà¢Õ¹ÇèÒ $u^3 + v^3$ à»ç¹ÃÒ¡¢Í§ÊÁ¡Òà $y^{2} + qy - \frac{p^{3}}{27} = 0$ ¹ÕèäÁè¶Ù¡¹Ð¤ÃѺ ·Õè¶Ù¡ µéͧà»ç¹ $u^3, v^3$ ¨Ðà»ç¹ÃÒ¡¢Í§ÊÁ¡Òà ... «Öè§ãªéá¹Ç¤Ô´¾×é¹°Ò¹·ÕèÇèÒ ÊÁ¡ÒáÓÅѧÊͧ·ÕèàÃÒÃÙé ¼ÅºÇ¡¢Í§ÃÒ¡ áÅÐ ¼Å¤Ù³¢Í§ÃÒ¡ ¤×Í $x^2 - (¼ÅºÇ¡¢Í§ÃÒ¡)x + ¼Å¤Ù³¢Í§ÃÒ¡ = 0$ ÊÓËÃѺµÑÇá»Ã¨ÐãªéµÑÇÍ×è¹·ÕèäÁèãªè x ¡çä´é |
#4
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¢Íº¤Ø³ÁÒ¡¤ÃѺà¢éÒã¨áÅéǤÃѺ áµè¾ÍËÒ$u,v$ ä´éáÅéǨÐä´éÃÒ¡¢Í§ÊÁ¡ÒÃàÅÂäËÁ¤ÃѺ
àËç¹¼ÁÍèÒ¹ã¹Ë¹Ñ§Ê×ÍÊÍǹ. ÁѹµéͧÁÕ ÃÒ¡»°Á°Ò¹ÁÒà¡ÕèÂÇ¢éͧáµèÍèÒ¹ÂѧäÁèà¢éÒã¨ÍèФÃѺ ÊÃØ»áÅéǾÍàÃÒÃÙé$u,v$ÊÒÁÒöµÍºä´éàÅÂäËÁ¤ÃѺ
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#5
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¡çà¾ÃÒÐÇèÒ à¹×èͧ¨Ò¡ $u^3, v^3$ à»ç¹¤ÓµÍº¢Í§ÊÁ¡Òà $y^2+qy+\frac{p^3}{27}=0$ ä§ÅèФÃѺ
¾Íä´é¤ÓµÍºÁÒµéͧ¡ÒÃËÒ $u,v$ ¡çµéͧ·Ó¡ÒöʹÃÒ¡·Õè 3 â´ÂÅͧᡡóմ٤ÃѺ¨Ðä´éµÒÁ·Õèà¢ÒÇèÒäÇé
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PaTa PatA pAtA Pon! |
#6
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¤×ÍÇèÒÂѧäÁè·ÃÒºÇèÒµÑÇàͧà¢éÒ㨨ÃÔ§æÃÖà»ÅèÒàÅÂÅͧ¨Ð·Ó´Ù¹Ð¤ÃѺ ¶éÒ¼Ô´µÃ§ä˹¾ÕèæªèǺ͡´éǹФÃѺ
⨷Â쨧ËÒ¤èÒx ¨Ò¡ÊÁ¡Òà $x^{3}-3x^{2}-3x-1=0 \text{¨Ñ´à»ç¹ÃÙ»} t^{3}+pt+q$ä´Â¡ÒÃá·¹ $x=t-\frac{b}{3a}$ ä´éà»ç¹ $t^{3}-6t-6=0$ ãËé $t=u+v\text{à»ç¹¤ÓµÍº¢Í§ÊÁ¡Òôѧ¡ÅèÒÇ á·¹¤èÒ} u^{3}+v^{3}+(3uv-6)(u+v)-6 =0$ µéͧ¡ÒÃãËé¡ÓÅѧ˹Öè§ËÁ´ä» ãËé $3uv-6=0,uv=2$ áÅСç¨Ðä´é $ u^{3}+v^{3}=6 $ à¹×èͧ¨Ò¡ $u^{4}áÅÐv^{3}$à»ç¹ÃÒ¡¢Í§ÊÁ¡ÒáéÒáÓÅѧÊͧÃÙ»·ÑèÇ仨Ðä´éÇèÒ $(y-u^{3})(y-v^{3}) =0 , y^{2}-(u^{3}+v^{3})y + u^{3}v^{3} =0$á·¹¤èÒ $ y^{2}-6y+8=0 $ ä´é $u=\sqrt[3]{2} \text{áÅÐ} v=\sqrt[3]{4}$ ´Ñ§¹Ñé¹ ä´é¤èÒx¤×Í u+v+1 «Ö觡ç¤×Í$\sqrt[3]{2}+\sqrt[3]{4}+1$ÃÖà»ÅèÒ¤ÃѺ áµèÊÁ¡ÒáÓÅѧÊÒÁµéͧÁÕ3µÑÇá»ÃäÁèãªèàËÃͤÃѺ §Ñ鹨ÐËÒÍÕ¡ÊͧµÑÇÂѧä§àËÃͤÃѺ
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#7
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$$x^3-3x^2-3x-1=0$$
By Mathematica $$ x=1+2^{1/3}+2^{2/3}$$ $$ x=1-\frac{1-i\sqrt3}{2^{1/3}}-\frac{1+i\sqrt3}{2^{2/3}}$$ $$ x=1-\frac{1-i\sqrt3}{2^{2/3}}-\frac{1+i\sqrt3}{2^{1/3}} $$
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âÅ¡¹ÕéÁÕ¤¹ÍÂÙè 10 »ÃÐàÀ· ¤×Í ¤¹·Õèà¢éÒã¨àÅ¢°Ò¹Êͧ áÅФ¹·ÕèäÁèà¢éÒ㨠|
#8
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·Õè¹éͧ·Ó ¶Ù¡µéͧáÅéǤÃѺ Åͧ·Ó´Ù«Ñ¡¢éÍÊͧ¢éÍãËé¾Íà¢éÒã¨ÇÔ¸Õ·Ó¡ç¾ÍáÅéǤÃѺ
âÍ¡ÒÊ·Õè¨ÐãªéÁÕ¹éÍÂÁÒ¡ ãËéÃÙéÇèÒÁÕÇÔ¸Õ¡ÒÃá¡éÍÂÙèã¹âÅ¡¹Õé¡çâÍठÅФÃѺ
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PaTa PatA pAtA Pon! |
#9
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ãËé $\omega ^3 = 1$ áÅÐ $\omega \not= 1$ (àªè¹ $\omega = \frac{-1+i \sqrt{3}}{2}$)
㹡óչÕé $u = 2^{1/3}$ áÅÐ $v = 4^{1/3}$ ¹Ñ蹡çËÁÒ¤ÇÒÁÇèÒ ¤èÒ $u$ ·Õèà»ç¹ä»ä´éÁÕ 3 ¤èÒ¤×Í $\sqrt[3]{2}\ ,\ \omega \sqrt[3]{2}\ ,\ \omega ^2 \sqrt[3]{2}$ 㹷ӹͧà´ÕÂǡѹ ¤èÒ $v$ ·Õèà»ç¹ä»ä´éÁÕ 3 ¤èÒ¤×Í $\sqrt[3]{4}\ ,\ \omega \sqrt[3]{4}\ ,\ \omega ^2 \sqrt[3]{4}$ ´Ñ§¹Ñé¹ $1+u+v$ à»ç¹ä»ä´é·Ñé§ËÁ´ $3 \times 3 = 9$ ÃٻẺ ¤×Í
¹Ñ蹤×ͤÙè¢Í§ $u,v$ ·ÕèÊÍ´¤Åéͧ¡Ñ¹¤×Í
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The difference between school and life? In school, you're taught a lesson and then given a test. In life, you're given a test that teaches you a lesson. |
#11
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ÍéÒÇàËç¹¹éͧ¾Ù´¶Ö§ $\omega$ 㹤ÇÒÁàËç¹´éÒ¹º¹ ¡ç¹Ö¡ÇèÒà¢éÒ㨷ÕèÁÒáÅéÇ«ÐÍÕ¡
·ÕèàÃÒà¢Õ¹ÇèÒ $\omega ^ 3 = 1$ áÅÐ $\omega \not= 1$ ¹Ñé¹ËÁÒ¤ÇÒÁÇèÒàÃÒµéͧ¡ÒÃãËé $\omega = 1^{1/3}$ â´Â·Õè $\omega \not= 1$ ¹Ñ蹡ç¤×Í $|\omega| = 1$ áÅÐ $\omega$ à»ç¹¨Ó¹Ç¹àªÔ§«é͹·ÕèÁÕ¢¹Ò´ÁØÁ $\frac{2\pi}{3}$ ËÃ×Í $\frac{4\pi}{3}$ àÃà´Õ¹ ËÃ×Íà¢Õ¹àµçÁæ¡ç¤×Í $\omega = \cos \frac{2\pi}{3} + i \sin \frac{2\pi}{3}$ ËÃ×Í $\omega = \cos \frac{4\pi}{3} + i \sin \frac{4\pi}{3}$ áÅéÇ $\omega$ ªèÇÂãËéÍÐäçèÒ¢Öé¹ËÃ×Íà»ÅèÒ àÁ×èÍàÃÒ¾Ù´¶Ö§ $\omega$ ·ÕèäÁèà¨ÒШ§¤èÒŧä»àÅÂÇèÒËÁÒ¶֧¤èÒä˹ áÅÐàÃÒäÁèÍÂÒ¡à¢Õ¹ãËé¤èÒµÔ´ã¹ÃٻẺ¢Í§¨Ó¹Ç¹àªÔ§«é͹ ¾ÃéÍÁ·Ñé§à¤Ã×èͧËÁÒÂÃÒ¡áÅÐàÈÉÊèǹµèÒ§æàµçÁä»ËÁ´ àÃÒÊÒÁÒöÍéÒ§¶Ö§ $1^{1/3}$ ·Ø¡¤èÒä´éÊÑé¹æ¤×Í $1^{1/3} = 1\ ,\ \omega\ ,\ \omega^2$ äÁèÇèÒàÃÒ¨ÐàÅ×Í¡ $\omega$ à»ç¹¤èÒä˹ ¡ç¨Ðä´é $\omega^2$ à»ç¹ÍÕ¡¤èÒ˹Öè§àÊÁÍ ã¹·Ó¹Í§à´ÕÂǡѹ àÃÒÊÒÁÒöÍéÒ§¶Ö§ $1^{1/5}$ ·Ø¡¤èÒä´éÊÑé¹æ¤×Í $1^{1/5} = 1\ ,\ \omega\ ,\ \omega^2\ ,\ \omega^3\ ,\ \omega^4$ 㹡óչÕé $\omega$ ¨Ðà»ç¹¤¹ÅеÑǡѺ´éÒ¹º¹ ¤×Í $\omega^5 = 1$ áÅÐ $\omega \not= 1$ áÅÐàªè¹à´ÕÂǡѹ äÁèÇèÒàÃÒ¨ÐàÅ×Í¡ $\omega$ à»ç¹¤èÒä˹ (¨Ò¡ $4$ ¤èÒ·Õèà»ç¹ä»ä´é) ¡ç¨Ðä´é $\{\omega\ ,\ \omega^2\ ,\ \omega^3\ ,\ \omega^4\}$ à»ç¹à«µà´ÔÁàÊÁÍ ÍÂèÒ§äáçµÒÁ ÁÕºÒ§¡Ã³Õ·Õè $\omega$ àÅ×͡ẺäÁèà¨ÒШ§äÁèä´é àªè¹ $\omega^4 = 1$ â´Â·Õè $\omega \not= 1$ ËÒ¡àÃÒàÅ×Í¡ $\omega = \cos \pi + i \sin \pi$ ¨Ð·ÓãËé $\omega^m$ à»ç¹ä´éà¾Õ§ $2$ ¤èÒ¤×Í $-1\ ,\ 1$ ´Ñ§¹Ñé¹ â´Â·ÑèÇä»àÃÒ¨Ö§àÅ×Í¡ $\omega$ ¤èҶѴÁÒ·ÕèäÁèãªè $1$ ËÃ×ÍËÁÒ¶֧ $\omega = \cos \frac{2 \pi}{n} + i \sin \frac{2 \pi}{n}$ àÁ×èÍàÃÒ¹Ó $\omega$ ÁÒãªé¡Ñº¡ÒÃÍéÒ§¶Ö§ $2^{1/3}$ ·Ø¡¤èÒÍÂèÒ§ÊÑé¹æ ¡ç¨Ðä´é $2^{1/3} = \sqrt[3]{2}\ ,\ \omega \sqrt[3]{2}\ ,\ \omega^2 \sqrt[3]{2}$ ËÃ×ÍÍéÒ§¶Ö§ $2^{1/5}$ ·Ø¡¤èÒÍÂèÒ§ÊÑé¹æ ¡ç¨Ðä´é $2^{1/5} = \sqrt[5]{2}\ ,\ \omega \sqrt[5]{2}\ ,\ \omega^2 \sqrt[5]{2}\ ,\ \omega^3 \sqrt[5]{2}\ ,\ \omega^4 \sqrt[5]{2}$
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The difference between school and life? In school, you're taught a lesson and then given a test. In life, you're given a test that teaches you a lesson. 27 ¸Ñ¹ÇÒ¤Á 2006 10:47 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ TOP |
#12
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àÃÕ¹·Õèä˹¤ÃѺ ÂÒ¡¨Ñ§ ÃÖÊÁѼÁàÃÕ¹äÁèÁÕÊ͹àÃ×èͧ¹Õé¡Ñ¹¹êÒ ËÅÑ¡ÊÙµÃãËÁèãªèÁÑéÂ
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ËÑÇ¢éÍ | ¼ÙéµÑé§ËÑÇ¢éÍ | Ëéͧ | ¤ÓµÍº | ¢éͤÇÒÁÅèÒÊØ´ |
Numerical Method ¤×ÍÍÐäà | SoRuJa | ¤³ÔµÈÒʵÃìÍØ´ÁÈÖ¡ÉÒ | 4 | 28 ¸Ñ¹ÇÒ¤Á 2006 12:54 |
Halley's Method | MaThNa | ¿ÃÕÊäµÅì | 2 | 04 ¡Ã¡®Ò¤Á 2005 11:47 |
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