题目内容
已知2a=3b=m,且![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_ST/0.png)
A.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_ST/1.png)
B.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_ST/2.png)
C.6
D.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_ST/3.png)
【答案】分析:根据已知条件可利用对数的性质分别求得
和
的表达式,进而根据
+
=2求得m的值.
解答:解:∵2a=3b=m
∴m>0
∵2a=m 3b=m
∴
=logm2,
=logm3
+
=logm2+logm3=logm6=2
∴m=![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/8.png)
故选A.
点评:本题主要考查了指数函数和对数函数的性质.考查了学生综合分析问题和解决问题的能力.
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/0.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/1.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/2.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/3.png)
解答:解:∵2a=3b=m
∴m>0
∵2a=m 3b=m
∴
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/4.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/5.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/6.png)
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/7.png)
∴m=
![](http://thumb.zyjl.cn/pic6/res/gzsx/web/STSource/20131101221344944430646/SYS201311012213449444306010_DA/8.png)
故选A.
点评:本题主要考查了指数函数和对数函数的性质.考查了学生综合分析问题和解决问题的能力.
![](http://thumb.zyjl.cn/images/loading.gif)
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