1 . 组合恒等式
,可以利用“算两次”的方法进行证明:分别求
和
的展开式中
的系数.前者
的展开式中
的系数为
;后者
的展开式
中
的系数为
.因为
,所以这两个展开式中
的系数相等,即
,请用“算两次”的方法化简式子
( )(其中
,
,
,
)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/587046866167198004c4860bf5aa45ae.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9848e2fdaa409da81971e4d9eadfe184.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9552f93a5ceccb3c9cb517436018b328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6fdf138124aba5204739cafbf1b59d47.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9848e2fdaa409da81971e4d9eadfe184.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6fdf138124aba5204739cafbf1b59d47.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5d85201cbf5f8984bd8c6a708ee87cc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9552f93a5ceccb3c9cb517436018b328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/079708d054f153a73724cc63dfcbe388.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6fdf138124aba5204739cafbf1b59d47.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8ea0570c8cca5cafb589fdf18c6bd3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0abb7dac8eba244c6b425d0b8fb52f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6fdf138124aba5204739cafbf1b59d47.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/092d5cf7ee736195147eed7aedf84d76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/875e5a9d9ba3ea3ec1aa55bd2f9ad4b4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b9f6b983ca589de1ecb4b7c70e6b052.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f093c61867ee4ce75f951d46b9b123.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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2021-07-13更新
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179次组卷
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2卷引用:北京市第八十中学2020-2021学年高二下学期期中考试数学试题