题目内容
设二次函数
,方程
的两根
和
满足
.
(1)求实数
的取值范围;
(2)试比较
与
的大小.并说明理由.
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135747690.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135762556.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135778300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135809331.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135840570.png)
(1)求实数
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135856278.png)
(2)试比较
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135871664.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135903364.png)
(Ⅰ)所求实数
的取值范围是
.
(II)
.
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135856278.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234136059633.png)
(II)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234136168932.png)
本话题主要是考查了二次函数的 性质和方程根的问题的综合运用。
(1)令
,
则由题意可得![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232341362461464.png)
求解得参数a的范围。
(2)方程![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135762556.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234136324256.png)
,由韦达定理得
,
,于是
得到结论。
(1)令
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234136230943.png)
则由题意可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232341362461464.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232341362771526.png)
(2)方程
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234135762556.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234136324256.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234136339726.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234136371554.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823234136480491.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232341366832333.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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