题目内容
在R上定义运算:![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_ST/0.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_ST/1.png)
A.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_ST/2.png)
B.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_ST/3.png)
C.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_ST/4.png)
D.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_ST/5.png)
【答案】分析:依定义将不等式
变为x2-x-(a2-a-2)≥1,整理得x2-x+1≥a2-a,对任意实数x成立,令(x2-x+1)min≥a2-a,解出a的范围即可求出其最大值.
解答:解:由定义知不等式
变为x2-x-(a2-a-2)≥1,
∴x2-x+1≥a2-a,对任意实数x成立,
∵x2-x+1=
≥![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/3.png)
∴a2-a≤![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/4.png)
解得
≤a≤![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/6.png)
则实数a的最大值为![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/7.png)
故应选D
点评:本题考查利用恒成立的关系构建关于参数的不等式及一元二次不等式的解法.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/0.png)
解答:解:由定义知不等式
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/1.png)
∴x2-x+1≥a2-a,对任意实数x成立,
∵x2-x+1=
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/2.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/3.png)
∴a2-a≤
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/4.png)
解得
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/5.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/6.png)
则实数a的最大值为
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131025123433531563517/SYS201310251234335315635004_DA/7.png)
故应选D
点评:本题考查利用恒成立的关系构建关于参数的不等式及一元二次不等式的解法.
![](http://thumb.zyjl.cn/images/loading.gif)
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