题目内容
(本小题满分13分)某沿海地区养殖的一种特色海鲜上市时间仅能持续5个月,预测上市初期和后期会因供应不足使价格呈持续上涨态势,而中期又将出现供大于求,使价格连续下跌.现有三种价格模拟函数:①
;②
;③
.(以上三式中
均为常数,且
)
(1)为准确研究其价格走势,应选哪种价格模拟函数(不必说明理由)
(2)若
,
,求出所选函数
的解析式(注:函数定义域是
.其中
表示8月1日,
表示9月1日,…,以此类推);
(3)在(2)的条件下研究下面课题:为保证养殖户的经济效益,当地政府计划在价格下跌期间积极拓宽外销,请你预测该海鲜将在哪几个月份内价格下跌.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022450973666.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022450988766.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451019817.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451035411.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451051385.png)
(1)为准确研究其价格走势,应选哪种价格模拟函数(不必说明理由)
(2)若
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451066513.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451082555.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451097447.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451113401.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451129367.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451144337.png)
(3)在(2)的条件下研究下面课题:为保证养殖户的经济效益,当地政府计划在价格下跌期间积极拓宽外销,请你预测该海鲜将在哪几个月份内价格下跌.
(1)
;(2)
;(3)在9月,10月两个月内价格下跌.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451019817.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408240224511751115.png)
试题分析:(1)利用价格呈现前几次与后几次均连续上升,中间几次连续下降的趋势,故可从三个函数的单调上考虑,前面两个函数没有出现两个递增区间和一个递减区间,应选f(x)=x(x-q)2+p为其模拟函数;(2)由题中条件:f(0)=4,f(2)=6,得方程组,求出p,q即可,从而得到f(x)的解析式;
(3)确定函数解析式,利用导数小于0,即可预测该果品在哪几个月份内价格下跌.
试题解析:(1)根据题意,应选模拟函数
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451019817.png)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451066513.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451082555.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408240224512531194.png)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408240224511751115.png)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451269867.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451285846.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451300778.png)
又
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451316566.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451331473.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451347617.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824022451363442.png)
所以可以预测这种海鲜将在9月,10月两个月内价格下跌.
![](http://thumb2018.1010pic.com/images/loading.gif)
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