2024高三·全国·专题练习
1 . 下面是应用公式
,求最值的三种解法,答案却各不同,哪个解答错?错在哪里?已知复数
为纯虚数,求
的最大值.
解法一:∵
,
又∵
是纯虚数,令
(
且
),
∴
.
故当
时,即当
时,所求式有最大值为
.
解法二:∵
,∴
.
故所求式有最大值为
.
解法三:∵
,
又∵
为纯虚数,∴
,
∴
.
故所求式有最大值为
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b24b1f5fe3cf65914e79532f4d2b23d2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e81e59019989b7dc2fb59b037ef6e010.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e3958fbc45ee3e72d9a6dc37a8f9474.png)
解法一:∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8201b70b4e9a66d8843dff2e728199c.png)
又∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e81e59019989b7dc2fb59b037ef6e010.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5cdecf72a044cbeb148db4e743c52514.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2dd0914dc4d4c7f75710ff460a286fcf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b03b011f69dfc5262a3d82f64676739b.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7794d59445d4545e6fd58d484fef86d3.png)
故当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a3c442579603164f3fc19458677d307.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/128730d6a25a11ed9b6b0f0e7f4f0433.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b7e9bd225e22d3c95a681720114056f.png)
解法二:∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a61f82d3db0076d8d07b901691021f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c186e2d43b0f52ff872a3613d56f8b1.png)
故所求式有最大值为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/934c6d8e32b31bdcfa263c705b95182b.png)
解法三:∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62981b55a133db7d326bef9d3e73b4c2.png)
又∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e81e59019989b7dc2fb59b037ef6e010.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed98359cf005d2b49ec68f55d1f87c6e.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c56d0e6036bae5d5a30c2a1f9fff19a0.png)
故所求式有最大值为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c296c04fc52c07364a234c0ac6233022.png)
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2 . 类比复数加法的几何意义,请写出复数减法的几何意义.
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2023-10-09更新
|
30次组卷
|
3卷引用:2.1 复数的加法与减法