原题呈现:若
,求a、b的值.
方法介绍:
①看到
可想到如果添上常数4恰好就是
,这个过程叫做“配方”,同理
,恰好把常数5分配完;
②从而原式可以化为
由平方的非负性可得
且
.
经验运用:
(1)若
,求
的值.
(2)当a,b,c分别取何值时,代数式
有最小值?并求其最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97032357a9c4b383ba78131e9d78aafb.png)
方法介绍:
①看到
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e302bac429b3ce3f8436e98ce181c22c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f79406cfd8be106da01686341f65903.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a55c8190e89385d04903a9c531393a17.png)
②从而原式可以化为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bbb42a21759ce75f7b759a2c3a585df0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7fcd645ddfcec6b46d9581a985452a04.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0aa6665c058b84c4df8821edb7eb6b7a.png)
经验运用:
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f08b8e2f252d6657404e3cf5e322201.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20d6fc9b90f370fbb27552876b650f8f.png)
(2)当a,b,c分别取何值时,代数式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f183aae086144af69f5b5c3419ad7fbd.png)
22-23七年级下·陕西西安·阶段练习 查看更多[2]
更新时间:2023-03-28 18:01:07
|
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适中
(0.65)
【推荐1】求下列各代数式的值;
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(1)若
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(2)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/757b9a87177ea6f76045c3e3eeff543a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fe6066b90a0b0f0fabcd47d0d7e9f67f.png)
您最近一年使用:0次
解答题-计算题
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适中
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【推荐1】计算:
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/921ef5abce73648e3834140df9a72aa8.png)
您最近一年使用:0次