名校
解题方法
1 . 如图所示,设矩形
(
)的周长为20厘米,把
沿
向
折叠,
折过去后交
于点
,设
厘米,
厘米.
![](https://img.xkw.com/dksih/QBM/2021/1/23/2642185204228096/2649240954798080/STEM/b0e37175-49fa-4e3a-8387-bb6254d188f6.png?resizew=250)
(1)证明:
;
(2)建立变量
与
之间的函数关系式
,并写出函数
的定义域;
(3)求
的最大面积以及此时的
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b9199a3de404cb13ae7710f73db5c8f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d7ac5396c5ea442e0364b50c1db3d2da.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8c7a3d679b4dae63575903387a76ce45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/457c6935fc4305838a02325c4e08017a.png)
![](https://img.xkw.com/dksih/QBM/2021/1/23/2642185204228096/2649240954798080/STEM/b0e37175-49fa-4e3a-8387-bb6254d188f6.png?resizew=250)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3f10d43c7f9892659868221560edd90.png)
(2)建立变量
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/51c530f4b7491b95acb8ce3eef9aa09d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/51c530f4b7491b95acb8ce3eef9aa09d.png)
(3)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3da7bcea5a45eeae211f5851f12a7517.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
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