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指數指的是冪運算 $a^n\left(a\mathrm{\ne }0\right)$

1. $a^{}$
   0 = 1 a^0 = 1
2. $a^n=$
   a × a × ⋯ × a a^n = a \times a \times \cdots \times a
3. $a^n = \frac 1 {a^{-n}}$

運演算法則

1. $a^n \cdot a^m = a^{n+m}$
2. $(a^n)^m = a^{nm}$
3. $\frac {a^n}{a^m} = a^{n-m}$
4. $(ab)^n = a^nb^n$
5. $a^{-m} = \frac 1 {a^m}$

與對數互為逆運算

$b = a^n <=> n = \log_ab$