【解析】
试题分析:
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020717-38239.png)
=
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020718-98852.png)
={4,-2}…………………………2分
因为 A
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020718-52658.png)
所以B=
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020719-35321.png)
或B={4},B={-2},B={4,-2}………………………4
当B=
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020719-35321.png)
时,
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020719-87242.png)
,得
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020719-37950.png)
……………………6
当B={4}时,即
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020719-16965.png)
得
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020719-91156.png)
所以无解…………………8
当B={-2}时,即
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020720-36682.png)
得a=4………………………..9
当B={4,-2}时,得a=-2………………………….10
综上: a= -2或a
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020718-70243.png)
或a<-4…………………12
考点:本题主要考查集合的运算,一元二次方程解的讨论。
点评:易错题,根据题中给定集合,从A
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020718-52658.png)
出发可得B=
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020719-35321.png)
或B={4},B={-2},B={4,-2}几种情况,其中B=
![](http://img.shitiku.com.cn/uploads/allimg/20200323/20200323020719-35321.png)
易被忽视。