Corrected the expansion of a number raised to a negative integer

latex/intro.tex

@@ -413,7 +413,7 @@ \subsection{Exponentials and Logarithms}
 \[
     b^x = \underbrace{b\times b\times \cdots \times b}_{x} \enspace .
 \]
-When $x$ is a negative integer, $b^x=1/b^{-x}$.  When $x=0$, $b^x=1$.
+When $x$ is a negative integer, $b^{-x}=1/b^{x}$.  When $x=0$, $b^x=1$.
 When $b$ is not an integer, we can still define exponentiation in terms
 of the exponential function $e^x$ (see below), which is itself defined in
 terms of the exponential series, but this is best left to a calculus text.