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算数算数70 views·Updated Jun 1, 2026·1 page

指数法則と指数関数の基本

指数関数って聞いたことある？実は君たちの身の回りにたくさん隠れているんだ。スマホのバッテリーの減り方、銀行の利息、さらには人口の増加まで、全部指数関数で説明できる。今日は有理数から実数へと指数を拡張して、この強力な数学ツールをマスターしよう！

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# 指数の拡張と指数関数 ## 1. 概要 - $a$を正の数とする時、$x$が有理数の時、$a^x$はすでに定義されている。この$a^x$の$x$を実数にまで拡張して、$a^x$を定義する事を考える。この$a^x$を指数関数という。指数関数は、微分積分学において重要な役割を

指数の拡張と指数関数の基礎

君がこれまで学んできた$2^3 = 8みたいな指数は、実はもっと広い世界への入り口なんだ。今度はみたいな指数は、実はもっと広い世界への入り口なんだ。今度は2^{1.5}やや2^{\sqrt{2}}$みたいに、指数が小数や無理数の場合も考えてみよう。

有理数は分数で表せる数（23\frac{2}{3}や−57-\frac{5}{7}など）で、無理数は分数では表せない数（2\sqrt{2}やπ\piなど）だ。この両方を合わせたものが実数になる。

指数関数f(x)=axf(x) = a^x（ただしa>0a > 0、a≠1a \neq 1）は、xxが実数全体で定義される関数だ。指数法則ax+y=ax⋅aya^{x+y} = a^x \cdot a^yや(ax)y=axy(a^x)^y = a^{xy}は今でも成り立つから安心して。

特に重要なのが**ネイピア数e≈2.71828e ≈ 2.71828**を底とする指数関数exe^xだ。これは微分してもexe^xのまま変わらないという魔法のような性質を持っている。

💡 ここがポイント！ 指数関数axa^xはa>0a > 0なら常に正の値になる。つまりグラフがx軸より下に行くことは絶対にないんだ！

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What is the Knowunity AI companion?

Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.

Where can I download the Knowunity app?

You can download the app in the Google Play Store and in the Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Most popular content in 算数

7

Most popular content

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Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.6/5App Store
4.7/5Google Play

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan SiOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha KlichAndroid user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

AnnaiOS user

算数算数70 views·Updated Jun 1, 2026·1 page

指数法則と指数関数の基本

指数関数って聞いたことある？実は君たちの身の回りにたくさん隠れているんだ。スマホのバッテリーの減り方、銀行の利息、さらには人口の増加まで、全部指数関数で説明できる。今日は有理数から実数へと指数を拡張して、この強力な数学ツールをマスターしよう！

1
of 1
# 指数の拡張と指数関数 ## 1. 概要 - $a$を正の数とする時、$x$が有理数の時、$a^x$はすでに定義されている。この$a^x$の$x$を実数にまで拡張して、$a^x$を定義する事を考える。この$a^x$を指数関数という。指数関数は、微分積分学において重要な役割を

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指数の拡張と指数関数の基礎

君がこれまで学んできた$2^3 = 8みたいな指数は、実はもっと広い世界への入り口なんだ。今度はみたいな指数は、実はもっと広い世界への入り口なんだ。今度は2^{1.5}やや2^{\sqrt{2}}$みたいに、指数が小数や無理数の場合も考えてみよう。

有理数は分数で表せる数（23\frac{2}{3}や−57-\frac{5}{7}など）で、無理数は分数では表せない数（2\sqrt{2}やπ\piなど）だ。この両方を合わせたものが実数になる。

指数関数f(x)=axf(x) = a^x（ただしa>0a > 0、a≠1a \neq 1）は、xxが実数全体で定義される関数だ。指数法則ax+y=ax⋅aya^{x+y} = a^x \cdot a^yや(ax)y=axy(a^x)^y = a^{xy}は今でも成り立つから安心して。

特に重要なのが**ネイピア数e≈2.71828e ≈ 2.71828**を底とする指数関数exe^xだ。これは微分してもexe^xのまま変わらないという魔法のような性質を持っている。

💡 ここがポイント！ 指数関数axa^xはa>0a > 0なら常に正の値になる。つまりグラフがx軸より下に行くことは絶対にないんだ！

We thought you’d never ask...

What is the Knowunity AI companion?

Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.

Where can I download the Knowunity app?

You can download the app in the Google Play Store and in the Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Most popular content in 算数

7

Most popular content

9

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.6/5App Store
4.7/5Google Play

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan SiOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha KlichAndroid user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

AnnaiOS user