题目内容
在二次根式①![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_ST/0.png)
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_ST/1.png)
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_ST/2.png)
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_ST/3.png)
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_ST/4.png)
A.①和③
B.②和③
C.①和④
D.③和④
【答案】分析:首先把上面的四个式子化成最简二次根式,再找出与
是同类二次根式的式子即可.
解答:解:∵①
=2
,
②
=2
,
③
=
,
④
=3
;
∴与
是同类二次根式的是①、④.
故选C.
点评:正确对根式进行化简,以及正确理解同类二次根式的定义是解决问题的关键.
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/0.png)
解答:解:∵①
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/1.png)
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/2.png)
②
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/3.png)
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/4.png)
③
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/5.png)
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/6.png)
④
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/7.png)
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/8.png)
∴与
![](http://thumb.zyjl.cn/pic6/res/czsx/web/STSource/20131103202004313247873/SYS201311032020043132478002_DA/9.png)
故选C.
点评:正确对根式进行化简,以及正确理解同类二次根式的定义是解决问题的关键.
![](http://thumb.zyjl.cn/images/loading.gif)
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