题目内容
已知![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_ST/0.png)
【答案】分析:利用完全平方公式先求出
和
的值,再代入计算.
解答:解:∵a+
=7,
∴
,
,
∴
+
=3,
+
=-3(不合题意舍去),
∴
=50.
点评:本题主要考查了利用完全平方公式化简二次根式的能力.
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/0.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/1.png)
解答:解:∵a+
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/2.png)
∴
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/3.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/4.png)
∴
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/5.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/6.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/7.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/8.png)
∴
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194137310997377/SYS201311031941373109973018_DA/9.png)
点评:本题主要考查了利用完全平方公式化简二次根式的能力.
![](http://thumb2018.1010pic.com/images/loading.gif)
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