如图1是一个长为
、宽为b的长方形,沿图中虚线用剪刀平均分成四块小长方形,然后用四块小长方形拼成一个“回形”正方形(如图2).
之间的等量关系是___________;
(2)根据(1)中的等量关系解决下面的问题;
①若
,则
_________;
②若
,求
的值.
(3)拓展应用:若
,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d2a7b13d95229e2e938514739054541.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/948d5c14e1244d7fd9758fdcaf1d9f50.png)
(2)根据(1)中的等量关系解决下面的问题;
①若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcb82bde8c81e4d11b98d85e3c030bdd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ba7a4e97b81050b4d1762769392ae8b.png)
②若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/14fcee58b15f32376617ef9748598efb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3394e3945b9919fffa326e52721ade5.png)
(3)拓展应用:若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/727c66e7897694a37620bcfa6cdf5a12.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3783f2c14e134f6da9b722dbd3f581cd.png)
23-24七年级下·四川成都·阶段练习 查看更多[6]
四川省成都市成都天府中学2023-2024学年七年级下学期4月月考数学试题山东省枣庄市滕州市鲍沟镇鲍沟中学2023-2024学年七年级下学期期中数学试题湖南省怀化市溆浦县第一中学2023-2024学年七年级下学期期中数学试题安徽省合肥市第四十二中学华南城分校2023-2024学年七年级下学期期中数学试题山东省威海市荣成市16校联盟(五四制)2023-2024学年六年级下学期期中考试数学试题(已下线)期末押题模拟卷(考试范围:湘教版七下全部内容)-备战2023-2024学年七年级数学下学期期末真题分类汇编(湖南专用)
更新时间:2024-04-09 12:50:20
|
【知识点】 通过对完全平方公式变形求值解读
相似题推荐
解答题-问答题
|
适中
(0.65)
【推荐1】完全平方公式经过适当的变形,可以解决很多数学问题.
例如:若
,
,求
的值.
解:∵
,
,
∴
,
.
∴
,
∴
.
根据上面的解题思路与方法解决下列问题:
,
,则
______;
(2)如图,C是线段
上的一点,分别以
,
为边向两侧作正方形
与正方形
,设
,两正方形的面积和为20,求
的面积.
例如:若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8792eaab0b6464e5d07436c64aa751a2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca27cc54ca0332245f5167488daa3408.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c925be255ca736a53b24d13ddede1a86.png)
解:∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8792eaab0b6464e5d07436c64aa751a2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca27cc54ca0332245f5167488daa3408.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd7a886d6491ae03887c2ecb74a86f59.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1172405a2686f2cdbdaef5a5142456c.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a63160327f1a19225ef344b35ebfa873.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eb6c334918a51cb6909f85bf1b71a95f.png)
根据上面的解题思路与方法解决下列问题:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9182d60213e94c38b2ce9eabf6f02546.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d73552080b72be89317eb60e9bef76c0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/163f46d77d5a036bc2543844afd54872.png)
(2)如图,C是线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b60c3b75ff1610956dfe9a9cd7692d03.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b9d54cbbf601f4583659771eb534997.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/305a88d4e0249bd16d48eda01331d2d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36691f0269294ecae8f00b7bce97756c.png)
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解答题-证明题
|
适中
(0.65)
【推荐2】我们可以通过类比联想,引申拓展研究典型题目,可达到解一题知一类的目的,下面是一个案例,请补充完整.
原题:如图1,点E、F分别在正方形
的边
上,
,连接
,则
,试说明理由.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/3/17/43036281-6e0c-4a8f-8557-9969ef97b4b5.png?resizew=386)
(1)思路梳理
∵
,∴把
绕点A逆时针旋转
至
,可使
与
重合.
∵
,
∴
,点F、D、G共线.
易证
_______其判断理由是______,可得
.
(2)类比引申
如图2,四边形
中,
,点E、F分别在边
上,
.
与
互补(
、
都不是直角),求证:
;
(3)联想拓展
如图3,在
中,
,点D、E均在边
上,且
.猜想
应满足的等量关系,并写出推理过程.若
,求
的最小值.
原题:如图1,点E、F分别在正方形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e5141e0c913ff7ea7787d48f7c1d984.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/192155e6a3aade305b76b1eb7c75e30c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c9af98a1a048b1e2f7c71e83c33498c.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/3/17/43036281-6e0c-4a8f-8557-9969ef97b4b5.png?resizew=386)
(1)思路梳理
∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e735a28578ba191da6d4f3b0f8e8729.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e742966e3711cfa53dce04022acf4bcc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c02b54dc6b3e1bb6544f47d4c8743fcf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3bbd6f0a0412d0f43ce1f7c1d530e56e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a4d67cda359da23b9879419ee4c60e4.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09b786297e18a79a55cfb976a1435ec7.png)
易证
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f55407ae397733ff0e5d8583ce92c22c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c9af98a1a048b1e2f7c71e83c33498c.png)
(2)类比引申
如图2,四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29e6d34a6997973a522c8cc450c8cd9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e5141e0c913ff7ea7787d48f7c1d984.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/192155e6a3aade305b76b1eb7c75e30c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/febc9a89d0d1c97b88c0f4acd32b4e67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c543c3ddc3723fde6bbfca3ea3b921b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/febc9a89d0d1c97b88c0f4acd32b4e67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c543c3ddc3723fde6bbfca3ea3b921b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c9af98a1a048b1e2f7c71e83c33498c.png)
(3)联想拓展
如图3,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/40975f7553d8cfa57951b568bae9c464.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c76805974fefbe166b90d260e822ab5a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bcad6212fc95ab4d47f4949dfa39dcd2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/629910cb5427d982742302d73ec1caf7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
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