#1
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àŢ¡¡ÓÅѧ
$(-25^{\frac{1}{2}})^2$ = ??
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#2
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$(-25^{\frac{1}{2}})^2 \not = \ ?? $ ¤ÃѺ ẺÇèÒ $ \ (-a)^2 = (-a)(-a) = a^2 \ $ ËÃ×Í $(-2)(-2) = 4 $ ´Ñ§¹Ñé¹ $ \ (-25^{\frac{1}{2}})^2 = (-25^{\frac{1}{2}})(-25^{\frac{1}{2}}) = 25$ ËÁÒÂà赯 $ \ - (25^{\frac{1}{2}})^2 = - 25 $
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ÁÒËÒ¤ÇÒÁÃÙéäÇéµÔÇËÅÒ¹ áµèËÅÒ¹äÁèàÍÒàÅ¢áÅéÇ à¢éÒÁÒ·ÓàÅ¢àÍÒÁѹÍÂèÒ§à´ÕÂÇ ¤ÇÒÁÃÙéà»ç¹ÊÔè§à´ÕÂÇ·ÕèÂÔè§ãËé ÂÔè§ÁÕÁÒ¡ ÃÙéÍÐäÃäÁèÊÙé ÃÙé¨Ñ¡¾Í (¡àÇ鹤ÇÒÁÃÙé äÁèµéͧ¾Í¡çä´é ËÒäÇéÁÒ¡æáËÅдÕ) (áµè¡çÍÂèÒãËéÁÒ¡¨¹·èÇÁËÑÇ àÍÒµÑÇäÁèÃÍ´) |
#3
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áµè¶éÒàÃÒ¤Ô´ÇÔ¸Õ·Õè ãªé¡ÓÅѧ$(\frac{1}{2})$(2) àÃÒ¡ç¨Ðä´é -25 äÁèãªèàËÃͤèÐ
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#4
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ÍéÒ§ÍÔ§:
¼ÁäÁèªÍºãªé¡ÓÅѧ ËÃ×ͶéÒ¨ÐÁͧã¹ÃÙ»¢Í§ÃÒ¡ $(-25^{\frac{1}{2}})$ ¡ç¤×Í $-\sqrt{25} = (-1) (\sqrt{25})$ $(-25^{\frac{1}{2}})^2= (-\sqrt{25})(-\sqrt{25}) = (-1)(\sqrt{25})(-1)(\sqrt{25}) = 25 $ ä˹æ¡çä˹áÅéÇ µÒÁ¤ÓÃéͧ¢Í Åͧãªé¡ÓÅѧ´Ù¡çä´é¤ÃѺ $(-25^{\frac{1}{2}})^2 = [(-1)(25^{\frac{1}{2}})]^2 = (-1)^2(25^{\frac{1}{2}})^2 = (1)(25^{\frac{2}{2}}) = (1)(25) = 25$
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ÁÒËÒ¤ÇÒÁÃÙéäÇéµÔÇËÅÒ¹ áµèËÅÒ¹äÁèàÍÒàÅ¢áÅéÇ à¢éÒÁÒ·ÓàÅ¢àÍÒÁѹÍÂèÒ§à´ÕÂÇ ¤ÇÒÁÃÙéà»ç¹ÊÔè§à´ÕÂÇ·ÕèÂÔè§ãËé ÂÔè§ÁÕÁÒ¡ ÃÙéÍÐäÃäÁèÊÙé ÃÙé¨Ñ¡¾Í (¡àÇ鹤ÇÒÁÃÙé äÁèµéͧ¾Í¡çä´é ËÒäÇéÁÒ¡æáËÅдÕ) (áµè¡çÍÂèÒãËéÁÒ¡¨¹·èÇÁËÑÇ àÍÒµÑÇäÁèÃÍ´) 16 ¡ØÁÀҾѹ¸ì 2010 15:33 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ banker |
#5
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ËÅÒ¤¹ªÍº Å×ÁÇèÒ
$ (-a)^n\not= -a^n$ |
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