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description: multiplicative identity╱🚧 under construction ->
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# 乘法單位元素 𝕝

[數學](../../../../math) ⟩ [數系](../../..) ⟩ [實數](../..) ⟩ [建造](..) ⟩ [乘法]() ⟩ 單位元素 $${\color{orange}\mathbf{𝕝}}$$&#x20;

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![](https://487293287-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M5-JmwIjjSzWft9bo8C%2Fuploads%2F6psqPGgFHguzM4yqLGH2%2Fdefinition%2081x31.png?alt=media\&token=4023cbcf-b720-4ff9-b90d-5fe6550be85e) 令 $${\color{orange}\mathbf{𝕝}} = (-\infty, 1) = \{ \ p \in {\color{orange}\mathbb{Q}} \ | \ p < 1 \ \}$$

:star: 注意： $${\color{orange}\mathbf{𝕝}} \in {\color{orange}\mathbb{R}}$$ （ :point\_right: 原因請參閱： [rational](../reals/rational "mention")）
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{% tab title="👥 相關" %}
* [nonnegative](nonnegative "mention")
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## 乘法單位元素性質 <a href="#properties" id="properties"></a>

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⑴ 若 $${\color{orange}a} \ge {\color{orange}\mathbb{𝟘}}$$ 則  $${\color{orange}\mathbf{𝕝}} \cdot {\color{orange}a} = {\color{orange}a} \cdot  {\color{orange}\mathbf{𝕝}} = {\color{orange}a}$$

⑵ &#x20;
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