解ï¼
ï¼1ï¼è®¾ä¸æ¬¡å½æ°è§£æå¼ä¸ºp=kx+bï¼7<=x<=12),ç±å¾åç¥å®è¿ï¼7,500ï¼ãï¼12,250ï¼ä¸¤ç¹
带å
¥è§£æå¼
500=7k+b
250=12k+b
èç«åè§£å¾ k= -50,b=850
å½æ°è§£æå¼ä¸º p=-50x+850ï¼7<=x<=12)
(2)令æ¯å¤©çè·å©ä¸ºyå
å y=x(-50x+850)-250-5(-50x+850)(7<=x<=12)
åç®
y=-50x^2+1100x-4500
æ ¹æ®é¢æ
y=-50x^2+1100x-4500=1350
æ´ç
x^2-22x+117=0
x=13æ9
å 为7<=x<=12
æ以13èå»ï¼x=9
å³è¦ä½¿è·å©ä¸º1350å
ï¼æ°´ä»·åºå®ä¸º9å
ï¼æ¤æ¶æ¯å¤©å¯å®åº 850-9x50=400桶水
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