题目内容
已知函数
的图象过原点,
,
,函数y=f(x)与y=g(x)的图象交于不同两点A、B。
(1)若y=F(x)在x=-1处取得极大值2,求函数y=F(x)的单调区间;
(2)若使g(x)=0的x值满足
,求线段AB在x轴上的射影长的取值范围;
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941004900.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941020398.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941051541.gif)
(1)若y=F(x)在x=-1处取得极大值2,求函数y=F(x)的单调区间;
(2)若使g(x)=0的x值满足
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941067410.gif)
(I)F(x)的单调递减区间为[-1,1],单调递增区间为![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941082572.gif)
(II)![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941098546.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941082572.gif)
(II)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941098546.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941113856.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941129699.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941145626.gif)
(I)y=F(x)在x=-1处取得极大值2
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941160750.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941160636.gif)
由(1)(2)(3)得a="3," b="0," c=-3
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941176509.gif)
由
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941191456.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941223360.gif)
由
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941238451.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941254282.gif)
∴F(x)的单调递减区间为[-1,1],单调递增区间为
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941082572.gif)
(II)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941285825.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941301776.gif)
由
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941316898.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941332663.gif)
设A(x1, y1),B(x2, y2)则
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941347973.gif)
线段AB在x轴上射影长
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231329413631099.gif)
由g(x)=0得
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941379526.gif)
由
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941410752.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823132941425544.gif)
![](http://thumb.zyjl.cn/images/loading.gif)
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