Exponent Combination Laws/Negative Power of Quotient

Theorem
Let $a, b \in \R_{>0}$ be (strictly) positive real numbers.

Let $x \in \R$ be a real number.

Let $a^x$ be defined as $a$ to the power of $x$.

Then:
 * $\paren {\dfrac a b}^{-x} = \paren {\dfrac b a}^x$