千米井
幼苗
共回答了26个问题采纳率:100% 举报
(1)当
![](https://img.yulucn.com/upload/d/92/d92c9bbdb3ba90c302895a581ad3de6b_thumb.jpg)
时,
![](https://img.yulucn.com/upload/0/70/070c6dc33fa50c8d6950e70ca140ad19_thumb.jpg)
;当
![](https://img.yulucn.com/upload/5/85/585ae21eb069e19c7b23b305c1485ff1_thumb.jpg)
时,
![](https://img.yulucn.com/upload/e/eb/eeb082630c2040d32b23ac53afac6d36_thumb.jpg)
;(2)2.4元;6.4元
试题分析:(1)由图,当
![](https://img.yulucn.com/upload/d/92/d92c9bbdb3ba90c302895a581ad3de6b_thumb.jpg)
时,y为恒值;当
![](https://img.yulucn.com/upload/5/85/585ae21eb069e19c7b23b305c1485ff1_thumb.jpg)
时,图象过点(3,2.4)、(5,4.4),可根据待定系数法求函数关系式;
(2)因为
![](https://img.yulucn.com/upload/9/f9/9f9f897319d60827ac554c839ba7c10a_thumb.jpg)
,所以根据AB段对应的函数即可得到结果;因为7>3,所以根据BC段对应的函数关系式即可得结果.
(1)当
![](https://img.yulucn.com/upload/d/92/d92c9bbdb3ba90c302895a581ad3de6b_thumb.jpg)
时,
![](https://img.yulucn.com/upload/0/70/070c6dc33fa50c8d6950e70ca140ad19_thumb.jpg)
;
当
![](https://img.yulucn.com/upload/5/85/585ae21eb069e19c7b23b305c1485ff1_thumb.jpg)
时,设函数关系式为
![](https://img.yulucn.com/upload/2/25/225931d5f4c03f8c3fb1a5a7b092eb65_thumb.jpg)
,
∵图象过点(3,2.4)、(5,4.4),
![](https://img.yulucn.com/upload/8/6e/86e306d39d6afaa9631df980cf481296_thumb.jpg)
,解得
![](https://img.yulucn.com/upload/d/6e/d6ea60fcc479cba3cdcd5f499fb0fe95_thumb.jpg)
,
![](https://img.yulucn.com/upload/2/51/251a478b2093fd993f49edfec01f6fcd_thumb.jpg)
y与t之间的函数关系式为
![](https://img.yulucn.com/upload/e/eb/eeb082630c2040d32b23ac53afac6d36_thumb.jpg)
;
(2)当
![](https://img.yulucn.com/upload/e/31/e3131406dae73eb306f6ebc426b4f485_thumb.jpg)
时,
![](https://img.yulucn.com/upload/0/70/070c6dc33fa50c8d6950e70ca140ad19_thumb.jpg)
元,
当
![](https://img.yulucn.com/upload/c/bc/cbc878494b70f5ee1235ec10ddf3c3fe_thumb.jpg)
时,
![](https://img.yulucn.com/upload/7/66/766457576711ea4af54f143f751e3a51_thumb.jpg)
元.
点评:此类题目的解决需仔细分析函数图象,从中找寻信息,利用待定系数法求出函数解析式,从而解决问题.
1年前
3