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à¤Ã×èͧÁ×ͧ͢ËÑÇ¢éÍ | ¤é¹ËÒã¹ËÑÇ¢é͹Õé |
#1
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ªèÇ´éǤÃѺàÃ×èͧâ´àÁ¹áÅÐàù¨ì
$y = \sqrt{\frac{x^2-2}{x-4} }$
$y = \sqrt{x+1} - \sqrt{x-1} $ ËÒâ´àÁ¹ä´éáÅéÇáµèËÒàù¨ìäÁäè´éÍФÃѺ ªèÇÂ˹è͹ФÃѺ 26 ÁԶعÒ¹ 2012 22:54 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ essket7 |
#2
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·ÕèµÔ´µÍ¹¹Õé¤×Í àù¨ì ÍФÃѺ
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#3
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26 ÁԶعÒ¹ 2012 23:23 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 3 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ polsk133 |
#4
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ã¤Ã¾Í¨ÐÁÕÇÔ¸Õ¤Ô´ºéÒ§¤ÃѺ µÔ´ÇÔ¸Õ¡ÒäԴÊͧ¢é͹Õé¹Ò¹ÁÒ¡¤ÃѺ T.T
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#5
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¢éÍÊͧ ËÅÑ¡¡Òä×Í á·¹ x=1 ä´éÃÙ· 2 ¶éÒá·¹ x ÁÒ¡¡ÇèÒ¹Õé¨Ðä´é¤èÒ¹éÍÂŧàÃ×èÍÂæ à¢éÒã¡Åé0 (áµèäÁè¶Ö§0á¹è¹Í¹ à¾ÃÒÐ x+1 > x-1)
»Å.áµèà¢Õ¹µÍº¹èÒ¨Ðà¢Õ¹ẺÍ×è¹ áÅéÇ¢éÍÍ×è¹à¢Õ¹ä»áººä˹ÍФÃѺÇÔ¸Õ¤Ô´ Êèǹ¢éÍ1.´Ùã¹ wolfram áÅéÇ¡é͹ãËè¨Ñ§ - -" 26 ÁԶعÒ¹ 2012 23:42 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ polsk133 |
#6
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¢Íº¤Ø³¤ÃѺ Êèǹ¢éÍ 1 ËÒàù¨ìä»äÁèà»ç¹¨ÃÔ§æ T.T ´Ùã¹ wolfram áÅéÇ¡çäÁèà¡ç· - -
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#7
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$y = \sqrt{x+1} - \sqrt{x-1} $
àÃÒÃÙéÇèÒ $x\geqslant 1 $ Åͧà¢Õ¹ $x$ ÁÒã¹à·ÍÁ¢Í§ $y$ áÅéǾԨÒóҤèҢͧ $y$ $y^2=2x-2\sqrt{x^2-1} $ $2\sqrt{x^2-1}=2x-y^2$ $4(x^2-1)=4x^2-4xy^2+y^4$ $y^4+4=4xy^2$ $x=\dfrac{y^4+4}{4y^2} \rightarrow y\not= 0$ á·¹¤èÒ $x\geqslant 1$ $\dfrac{y^4+4}{4y^2}\geqslant 1$ $y^4-4y^2+4\geqslant0$ $(y^2-2)^2\geqslant0$ à´ÕëÂÇÁÒäÅèµèÍ´Ùá»Å¡æ´Õ ¹èÒ¨Ðà»ç¹¼Å¾Ç§¨Ò¡¡Òá¡ÓÅѧÊͧà¾×èÍ¢¨Ñ´¾¨¹ì $x$ ã¹¡Ã³ì ¢ÍäÅè´ÙÍÕ¡·Õ
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"¶éÒàÃÒÅéÁºèÍÂæ ã¹·ÕèÊØ´àÃÒ¨ÐÃÙéÇèÒ¶éÒ¨ÐÅéÁ ÅéÁ·èÒä˹¨Ðà¨çº¹éÍ·ÕèÊØ´ áÅÐÃÙéÍÕ¡ÇèÒµèÍä»·ÓÂѧ䧨ÐäÁèãËéÅéÁÍÕ¡ ´Ñ§¹Ñ鹨§ÍÂèÒ¡ÅÑÇ·Õè¨ÐÅéÁ"...ÍÒ¨ÒÃÂìÍӹǠ¢¹Ñ¹ä·Â ¤ÃÑé§áá㹪ÕÇÔµ·ÕèÊͺ¤³ÔµÊÁÒ¤Á¤³ÔµÈÒʵÃìàÁ×èÍ»Õ2533...¼Áä´éá¤è24¤Ðá¹¹(¨Ò¡ÃéͤÐá¹¹) 27 ÁԶعÒ¹ 2012 14:28 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 3 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ ¡ÔµµÔ |
#8
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¨Ò¡ $\left(\,\sqrt{x+1} - \sqrt{x-1}\right)\left(\,\sqrt{x+1}+\sqrt{x-1} \right) =2 $
$\sqrt{x+1} - \sqrt{x-1}=\dfrac{2}{\sqrt{x+1}+\sqrt{x-1} } =y$ ´Ñ§¹Ñ鹤èÒ $y$ ÁÒ¡·ÕèÊØ´àÁ×èÍ $\sqrt{x+1}+\sqrt{x-1}$ ÁÕ¤èÒ¹éÍ·ÕèÊØ´ «Öè§àÃÒ·ÃÒºáÅéÇÇèÒ $x\geqslant 1$ ´Ñ§¹Ñé¹ $\sqrt{x+1}+\sqrt{x-1}$ ÁÕ¤èÒ¹éÍ·ÕèÊØ´àÁ×èÍ $x=1$ à·èҡѺ $\sqrt{2} $ ¨Ðä´éÇèÒ $y$ ÁÕ¤èÒÁÒ¡·ÕèÊØ´¤×Í $\sqrt{2}$ ¤èÒ¹éÍÂÊØ´¤×Í $y>0$ ä´éàù¨ì¤×Í $\left(\,0\right.,\left.\,\sqrt{2} \right] $
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"¶éÒàÃÒÅéÁºèÍÂæ ã¹·ÕèÊØ´àÃÒ¨ÐÃÙéÇèÒ¶éÒ¨ÐÅéÁ ÅéÁ·èÒä˹¨Ðà¨çº¹éÍ·ÕèÊØ´ áÅÐÃÙéÍÕ¡ÇèÒµèÍä»·ÓÂѧ䧨ÐäÁèãËéÅéÁÍÕ¡ ´Ñ§¹Ñ鹨§ÍÂèÒ¡ÅÑÇ·Õè¨ÐÅéÁ"...ÍÒ¨ÒÃÂìÍӹǠ¢¹Ñ¹ä·Â ¤ÃÑé§áá㹪ÕÇÔµ·ÕèÊͺ¤³ÔµÊÁÒ¤Á¤³ÔµÈÒʵÃìàÁ×èÍ»Õ2533...¼Áä´éá¤è24¤Ðá¹¹(¨Ò¡ÃéͤÐá¹¹) |
#9
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$y = \sqrt{\dfrac{x^2-2}{x-4} }$
$\therefore y\geqslant 0$ $y^2=\dfrac{x^2-2}{x-4}$ $y^2x-4y^2=x^2-2$ $x^2-y^2x+4y^2-2=0$ $x=\dfrac{y^2\pm \sqrt{y^4-4(4y^2-2)} }{2} $ $\therefore y^4-4(4y^2-2)\geqslant 0$ $y^4-16y^2+8\geqslant 0$ $(y^2-8)^2-56\geqslant 0$ $(y^2-8+\sqrt{56} )(y^2-8-\sqrt{56} )\geqslant 0$ $(y^2-(\sqrt{8-\sqrt{56} })^2 )((y^2-(\sqrt{8+\sqrt{56} })^2)\geqslant 0$ $(y+\sqrt{8-\sqrt{56} })(y-\sqrt{8-\sqrt{56} })(y+\sqrt{8+\sqrt{56} })(y-\sqrt{8+\sqrt{56} })\geqslant 0$ $\because y\geqslant 0$ $\therefore (y-\sqrt{8-\sqrt{56} })(y-\sqrt{8+\sqrt{56} })\geqslant 0$ $0\leqslant y\leqslant \sqrt{8-\sqrt{56} } $ or $y\geqslant \sqrt{8+\sqrt{56} }$ |
#10
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ÍéÒ§ÍÔ§:
¨Ò¡ $\left(\,\sqrt{x+1} - \sqrt{x-1}\right)\left(\,\sqrt{x+1}+\sqrt{x-1} \right) =2 $ 2 ä´é¨Ò¡¡ÒÃá·¹¤èÒ x =1 à¹×èͧ¨Ò¡ x ÁÒ¡¡ÇèÒà·èҡѺ 1 ãªèäËÁ¤ÃѺ áÅéÇÊÁ¡ÒùÕéä´éÁÒÂѧä§ËÃͤÃѺ 27 ÁԶعÒ¹ 2012 19:01 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 2 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ essket7 |
#11
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ÁÒ¨Ò¡¼ÅµèÒ§¡ÓÅѧÊͧ¤ÃѺ
$(x+1)-(x-1)=2$ ¡ÃШÒÂà»ç¹ $\left(\,\sqrt{x+1} - \sqrt{x-1}\right)\left(\,\sqrt{x+1}+\sqrt{x-1} \right) =2 $ ÊÓËÃѺ¤èÒ $y$ ¼ÁÍÒ¨à¢Õ¹Ëéǹæä» ÍÂèÒ§·Õè¤Ø³polsk133ºÍ¡äÇéÇèÒ $x+1>x-1$ ´Ñ§¹Ñé¹ $y>0$
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"¶éÒàÃÒÅéÁºèÍÂæ ã¹·ÕèÊØ´àÃÒ¨ÐÃÙéÇèÒ¶éÒ¨ÐÅéÁ ÅéÁ·èÒä˹¨Ðà¨çº¹éÍ·ÕèÊØ´ áÅÐÃÙéÍÕ¡ÇèÒµèÍä»·ÓÂѧ䧨ÐäÁèãËéÅéÁÍÕ¡ ´Ñ§¹Ñ鹨§ÍÂèÒ¡ÅÑÇ·Õè¨ÐÅéÁ"...ÍÒ¨ÒÃÂìÍӹǠ¢¹Ñ¹ä·Â ¤ÃÑé§áá㹪ÕÇÔµ·ÕèÊͺ¤³ÔµÊÁÒ¤Á¤³ÔµÈÒʵÃìàÁ×èÍ»Õ2533...¼Áä´éá¤è24¤Ðá¹¹(¨Ò¡ÃéͤÐá¹¹) 27 ÁԶعÒ¹ 2012 20:10 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ ¡ÔµµÔ |
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