ÌâÄ¿ÄÚÈÝ
11£®Ä³½¡Éí²úÆ·ÆóÒµµÚÒ»Åú²úÆ·AÉÏÊÐÏúÊÛ£¬40ÌìÄÚÈ«²¿ÊÛÍ꣮¸ÃÆóÒµ¶ÔµÚÒ»Åú²úÆ·AÉÏÊкóµÄÊг¡ÏúÊÛ½øÐе÷ÑУ¬Çé¿ö·´À¡´ó¸ÅÈçͼ£¨1£©¡¢£¨2£©Ëùʾ£®ÆäÖÐÊг¡µÄÈÕÏúÊÛÁ¿£¨µ¥Î»£ºÍò¼þ£©ÓëÉÏÊÐʱ¼ä£¨Ì죩µÄ¹Øϵ½üËÆÂú×ãͼ£¨1£©ÖеÄÅ×ÎïÏߣ»Ã¿¼þ²úÆ·AµÄÏúÊÛÀûÈó£¨Ôª/¼þ£©ÓëÉÏÊÐʱ¼ä£¨Ì죩µÄ¹Øϵ½üËÆÂú×ãͼ£¨2£©µÄÕÛÏߣ®£¨¢ñ£©Ð´³öÊг¡µÄÈÕÏúÊÛÁ¿f£¨t£©ÓëµÚÒ»Åú²úÆ·AÉÏÊÐʱ¼ätµÄ¹Øϵʽ£»
£¨¢ò£©µÚÒ»Åú²úÆ·AÉÏÊкóµÄµÚ¼¸Ì죬Õâ¼ÒÆóÒµÈÕÏúÊÛÀûÈó×î´ó£¬×î´óÀûÈóÊǶàÉÙ£¿
·ÖÎö £¨¢ñ£©ÀûÓôý¶¨ÏµÊý·¨½áºÏÒ»Ôª¶þ´Îº¯ÊýµÄÐÔÖʼ´¿É£»
£¨¢ò£©Çó³öÀûÈóº¯ÊýµÄ½âÎöʽ£¬½áºÏÒ»Ôª¶þ´Îº¯ÊýµÄµ¥µ÷ÐÔ½øÐÐÇó½â¼´¿É£®
½â´ð ½â£º£¨1£©ÓÉͼÏóÖªÅ×ÎïÏߵĶԳÆÖáΪx=20£¬¶¥µã×ø±êΪ£¨20£¬60£©£¬
Å×ÎïÏß¿ª¿ÚÏòÏ£¬
ÔòÉèf£¨t£©=a£¨t-20£©2+60£¬
¡ßÅ×ÎïÏß¹ýԵ㣬
¡àf£¨0£©=400a+60=0£¬½âµÃa=-$\frac{3}{20}$£¬
Ôòf£¨t£©=-$\frac{3}{20}$£¨t-20£©2+60£¬£¨0¡Üt¡Ü40£¬t¡ÊN£©£®
£¨2£©ÏúÊÛÀûÈóy=$\left\{\begin{array}{l}{2t£¬}&{0¡Üt£¼30}\\{60£¬}&{30¡Üt¡Ü40}\end{array}\right.$£¬
ÔòÈÕÏúÊÛÀûÈó¦Õ£¨t£©=$\left\{\begin{array}{l}{-\frac{3}{10}£¨t-20£©^{2}•t+120t£¬}&{0¡Üt¡Ü30}\\{60[-\frac{3}{20}£¨t-20£©^{2}+60]£¬}&{30¡Üt¡Ü40}\end{array}\right.$£¬£¨t¡ÊN£©£®
¢Ùµ±0¡Üt¡Ü30ʱ£¬Áî¦Õ¡ä£¨t£©=-$\frac{9}{10}$t2+24t£¬
Óɦա䣨t£©=-$\frac{9}{10}$t2+24t£¾0µÃ0£¼t£¼$\frac{80}{3}$£¬
Óɦա䣨t£©=-$\frac{9}{10}$t2+24t£¼0µÃ$\frac{80}{3}$£¼t£¼30£¬
µ«t=$\frac{80}{3}$∉N£¬
ÓÖµ±t=26ʱ£¬¦Õ£¨26£©=2839.2£¬
µ±t=27ʱ£¬¦Õ£¨27£©=2843.1£¬¡£¨10·Ö£©
¢Úµ±30£¼t¡Ü40ʱ£¬¦Õ£¨t£©£¼¦Õ£¨30£©=2700
¹ÊµÚ27ÌìÏúÊÛÀûÈó×î´ó£¬×î´óÀûÈóÊÇ2843.1ÍòÔª¡£¨12·Ö£©
µãÆÀ ±¾ÌâÖ÷Òª¿¼²é첺¯ÊýµÄÓ¦ÓÃÎÊÌ⣬ÀûÓôý¶¨ÏµÊý·¨½áºÏÒ»Ôª¶þ´Îº¯ÊýµÄÐÔÖÊÊǽâ¾ö±¾ÌâµÄ¹Ø¼ü£®
A£® | 9 | B£® | 100 | C£® | 135 | D£® | 80 |
µÚ1ÁÐ | µÚ2ÁÐ | µÚ3ÁÐ | µÚ4ÁÐ | µÚ5ÁÐ | |
µÚ1ÐÐ | 1 | 3 | 5 | 7 | |
µÚ2ÐÐ | 15 | 13 | 11 | 9 | |
µÚ3ÐÐ | 17 | 19 | 21 | 23 | |
µÚ4ÐÐ | 31 | 29 | 27 | 25 | |
µÚ5ÐÐ | 39 | 37 | 35 | 33 | |
¡ | ¡ | ¡ | ¡ | ¡ | ¡ |
A£® | 505 | B£® | 506 | C£® | 254 | D£® | 253 |