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- 11-10-31 23:11
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1>a>b>0 ¿¡¼
f(a,b)=[[{(1/2)-(1/2a)-ln(b/a)}*(b^2)]+(1-a)*b] ÀÇ ÃÖ´ë°ªÀ» ±¸ÇÏ´Â ¹®Á¦¿´ÁÒ?
ÃÖ´ë/ÃÖ¼Ò°ªÀÌ¾ß ¾ðÁ¦³ª ±ØÁ¡ ¾Æ´Ï¸é °æ°èÁ¡¿¡ ³ªÅ¸³´Ù´Â °Ç ¾Æ½Ç °Å¶ó ¹Ï°í.
1. ¸ÕÀú °æ°èÁ¡¿¡¼ ¾îÂî µÇ³ª º¾´Ï´Ù.
1) b=0¿¡¼± Àú ÇÔ¼ö´Â ¹«Á¶°Ç 0.
2) a=b¿¡¼ a=1/2ÀÏ ¶§ ÃÖ´ë°ª 1/8
3) a=1¿¡¼ a=1/\sqrt{e}ÀÏ ¶§ ÃÖ´ë°ª 1/(2e)
2. ³»ºÎ¿¡¼ ¾îÂî µÇ³ª º¾´Ï´Ù.
f´Â Á¤ÀÇ¿ª¿¡¼ ¹ÌºÐ°¡´ÉÇϹǷΠ³»ºÎ¿¡ ±ØÁ¡ÀÌ ÀÖ´Ù¸é ±×·¡µð¾ðÆ®°¡ 0ÀÏ °Ì´Ï´Ù. Áï D_1f=D_2f=0.
D_1f=0ÀÌ µÇ´Â (a,b)ÀÇ °ü°è¸¦ ±¸Çغ¸¸é b=(2a^2+a )/(2a+1) Àε¥,
D_2f=0ÀÌ µÇ´Â (a,b)¸¦ Á÷Á¢ ±¸Çϱâ´Â ¾î·Á¿ì¹Ç·Î(½ÇÀº ºÒ°¡´É)
f(a,b)¿¡ b´ë½Å À§ a¿¡ ´ëÇÑ ÇÔ¼ö¸¦ Á÷Á¢ ´ëÀÔÇÏ¿© MAPLEÀ» ÀÌ¿ëÇÏ¿© ±×·¡ÇÁ¸¦ ±×·Áº¾´Ï´Ù.
±Ùµ¥, ÀÌ ¶§ ³ª¿À´Â ÃÖ´ë°ªÀÌ À§ °æ°è¿¡¼ ³ª¿À´Â ÃÖ´ë°ª 1/(2e)¿Í °ÅÀÇ Â÷ÀÌ°¡ ¾ø¾î¼ À°¾ÈÀ¸·Î Ãִ븦 °áÁ¤ÇϱⰡ ¸¸¸¸Ä¡ ¾Ê³×¿ä.-_-;;
(¹Ì¼¼ÇÏ°Ô³ª¸¶ ³»ºÎ ÃÖ´ë°ªÀÌ ÂɲûÀº ´õ Ä¿º¸À̱ä ÇÕ´Ï´Ù¸¸, Á¦´«ÀÌ »ß²ÙÀÏ ¼öµµ ÀÖÀ½)
¾ÏÆ°°£¿¡,
¾îµð¼ ÃÖ´ë°ªÀÌ ³ª¿À´ÂÁö°¡ ±Ã±ÝÇϸé D_2f(a,b)¿¡ Àú °ü°è½ÄÀ» ´ëÀÔÇؼ ±×·Áº¸´Â ¼ö¹Û¿¡ ¾ø½À´Ï´Ù. ¿©±â¿¡ ¼öÄ¡Çؼ®ÀûÀÎ ¹æ¹ýÀ» µ¿¿øÇÏ¿©(º°°Ô ¾Æ´Ï¶ó, Å×ÀÏ·¯ ´ÙÇ×½Ä µîÀ» µ¿¿øÇÏ¿© ´äÀ» ¾î¸²ÁüÀÛÇÑ´Ù´Â ¾ê±âÁÒ) ±Ù»ç°ª Á¤µµ ±¸ÇÏ´Â ¼±¿¡¼ ¸¶¹«¸®Áö¾î¾ß ÇÕ´Ï´Ù.
´äÀÌ ¿µ ¸¾¿¡ ¾È µéÁÒ? ¾î¿ ¼ö ¾ø¾î¿ä-_-;;;
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