题目内容
已知关于
的一元二次函数![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832050816.png)
(Ⅰ)设集合
和
,分别从集合
和
中随机取一个数作为
和
,求函数
在区间[
上是增函数的概率;
(Ⅱ)设点
是区域
内的随机点,记
有两个零点,其中一个大于
,另一个小于![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832424206.png)
,求事件
发生的概率
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211831956266.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832050816.png)
(Ⅰ)设集合
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832112651.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832175768.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832175289.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832222333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832315283.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832331299.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832346561.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832362473.png)
(Ⅱ)设点
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832378476.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832393997.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832409686.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832424206.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832424206.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832502277.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832534300.png)
(Ⅰ)∵函数
的图象的对称轴为![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832643602.png)
要使
在区间
上为增函数,
当且仅当
且
………………………………2分
若
则
,若
则
若
则
……………………4分
记
函数
在区间
上是增函数![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832502277.png)
则事件
包含基本事件的个数是1+2+2=5,∴
……6分
(Ⅱ)依条件可知试验的全部结果所构成的区域为
,
其面积
……………………………………8分
事件
构成的区域: ![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232118334543466.png)
由
,得交点坐标为
………………………………10分
,∴事件
发生的概率为![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232118336261145.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832549808.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832643602.png)
要使
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832549808.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832674473.png)
当且仅当
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832705398.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832830803.png)
若
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832846337.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832986361.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833002386.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833017404.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833236391.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833017404.png)
记
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833314386.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833329600.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833345509.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832502277.png)
则事件
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833376309.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833392693.png)
(Ⅱ)依条件可知试验的全部结果所构成的区域为
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232118334071590.png)
其面积
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833423816.png)
事件
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832534300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232118334543466.png)
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833501943.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211833516654.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232118335481287.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823211832534300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232118336261145.png)
略
![](http://thumb2018.1010pic.com/images/loading.gif)
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