题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015903-54650.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015903-88612.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015903-67443.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015904-62711.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015904-47130.png)
(1)若
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015903-54650.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015903-88612.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015904-65105.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015904-44970.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015905-30864.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015905-17573.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015905-24661.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015904-65105.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015905-74549.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015905-30075.png)
解析
试题分析:(1)方程有实数解,
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-27171.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-78982.png)
依题意,
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-64968.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-91613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-43567.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-12887.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-46843.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-48155.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-29697.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-91613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-43567.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-12887.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-46843.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-48155.png)
所以,“投掷两枚均匀骰子出现的点数”共有
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015908-90879.png)
当且仅当“
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-64968.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-29697.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-91613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-43567.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015908-34817.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-29697.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-91613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015908-29765.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015907-29697.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-78982.png)
所以满足
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015906-78982.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015908-99056.png)
从而
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015908-66790.png)
(2)在平面直角坐标系
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015909-46120.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015909-55791.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015909-96396.png)
正方形边长即直线
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015909-45112.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015909-41427.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015910-51046.png)
正方形的面积
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015910-33724.png)
圆
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015910-98871.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015910-13758.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015911-70855.png)
点评:古典概型概率需找到所有基本事件种数与满足题意要求的基本事件种数,然后求其比值,几何概型概率一般找的是长度比面积比或体积比
核心考点
试题【(本小题满分12分)、是常数,关于的一元二次方程有实数解记为事件.(1)若、表示投掷两枚均匀骰子出现的点数,求;(2)若、,且,求.】;主要考察你对古典概型的概念及概率等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015858-18906.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015858-39744.png)
A.![]() | B.![]() | C.![]() | D.![]() |
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015847-63278.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015848-89823.png)
A.![]() | B.![]() | C.![]() | D.![]() |
甲打靶射击,有4发子弹,其中有一发是空弹(“空弹”即只有弹体没有弹头的子弹).
(1)如果甲只射击
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015840-17750.png)
(2)如果甲共射击
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015840-78706.png)
(3)如果在靶上画一个边长为
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015840-15943.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015841-69425.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015841-63796.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015841-63796.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191027/20191027015841-63796.png)
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