题目内容
已知正整数a,b满足4a+b=30,则使得
+
取最小值时的实数对(a,b)
是 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044611959285.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044611959266.png)
是 ( )
A.(5,10) | B.(6,6) |
C.(10,5) | D.(7,2) |
A
选A.
+
=
=
≥
=
,当且仅当
=
且4a+b=30,即a=5,b=10时,
+
取最小值.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044611959285.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044611959266.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044612021734.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044612037841.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408240446120521123.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044612068335.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044612084307.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044612099362.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044611959285.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824044611959266.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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题目内容
A.(5,10) | B.(6,6) |
C.(10,5) | D.(7,2) |