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Power Laws

Power laws are among the most important and useful concepts in mathematics. They assist us in simplifying and solving complex mathematical expressions.

They find applications in many areas of mathematics, as well as in physics, engineering, and other natural sciences.

Basics

$$ \begin{aligned} a^n &= a \cdot a \cdot a \dots a\\[7pt] \text{For } a \neq 0 \text{, we have:}\quad a^0 &= 1,\quad a^{-n}=\dfrac{1}{a^n}\\[7pt] \text{For } a > 0 \text{, we have:}\quad a^b &= e^{b \cdot \ln(a)} \end{aligned} $$

Powers with the Same Base

$$ \begin{aligned} a^m \cdot a^n &= a^{(m+n)}\\[7pt] \dfrac{a^m}{a^n} &= a^{(m-n)} \end{aligned} $$

Examples:

$$ \begin{alignat}{7} 3^2 \cdot 3^4 &= a^{(2+4)} = 3^6 = 729\\[7pt] \dfrac{5^4}{5^2} &= 5^{(4-2)} = 5^2 = 25 \end{alignat} $$

Powers with the Same Exponent

$$ \begin{aligned} a^n \cdot b^n &= (a \cdot b)^n\\[7pt] \dfrac{a^n}{b^n} &= \Bigl(\dfrac{a}{b}\Bigr)^n \end{aligned} $$

Examples:

$$ \begin{aligned} 2^3 \cdot 4^3 &= (2 \cdot 4)^3 = 8^3 = 512\\[7pt] \dfrac{8^5}{4^5} &= \Bigl(\dfrac{8}{4}\Bigr)^5=2^5=32 \end{aligned} $$

Raising Powers to Powers

$$ \begin{aligned} \Bigl(a^m\Bigr)^n &= \Bigl(a^n\Bigr)^m =a^{(m \cdot n)} \end{aligned} $$

Example:

$$ \begin{aligned} \Bigl(2^4\Bigr)^3 &= 2^{(4 \cdot 3)} = 2^{12} = 4096 \end{aligned} $$