题目内容
下列极限正确的个数是( )①
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_ST/0.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_ST/1.png)
②
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_ST/2.png)
③
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_ST/3.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_ST/4.png)
④
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_ST/5.png)
A.2
B.3
C.4
D.都不正确
【答案】分析:由
qn=
知②不正确.由极限的概念知①③④成立.
解答:解:①n→∞,nα→∞,
→∞,∴![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/3.png)
=0(α>0),故①正确.
②
qn=
,由此可知②不正确.其它三个都正确.
③![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/7.png)
=
,故③成立.
④
C=C(C为常数).显然成立.
故选B.
点评:本题考查极限的概念,解题要认真审题,仔细解答.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/0.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/1.png)
解答:解:①n→∞,nα→∞,
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/2.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/3.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/4.png)
②
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/5.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/6.png)
③
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/7.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/8.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/9.png)
④
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131023213217248743633/SYS201310232132172487436000_DA/10.png)
故选B.
点评:本题考查极限的概念,解题要认真审题,仔细解答.
![](http://thumb.zyjl.cn/images/loading.gif)
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