由题意可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161136888563.gif)
;由
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161136904442.gif)
可得2-k<a<4-k,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161136935649.gif)
........................................................................................ .........4分
(1)当k=1时,
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161136951445.gif)
,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161136966696.gif)
故
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161136842698.gif)
.........................................................................................9分
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161136826300.gif)
的充分不必要条件,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161137060263.gif)
的充分不必要条件...................................11分
则
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161137154607.gif)
,解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823161136873293.gif)
,...........................................14分