\begin{frame}
  \frametitle{Exponential Functions}
  
  \begin{block}{}
    An \emph{exponential function} is a function of the form
    \begin{talign}
      f(x) = a^x
    \end{talign}
    where the \emph{base} $a$ is positive real number ($a > 0$).  
  \end{block}
%   \pause
  
  \begin{center}
  \begin{minipage}{.45\textwidth}
  \scalebox{.7}{
  \begin{tikzpicture}[default,baseline=0cm]
    \diagram{-2.5}{2.5}{-1}{4}{1}
    \diagramannotatez
    \diagramannotatexx{-1,1}
    \diagramannotatey{1}
    \begin{scope}[ultra thick]
    \draw[cgreen] plot[smooth,domain=-2.5:2,samples=300] (\x,{2^\x});
    \end{scope}
  \end{tikzpicture}
  }\\[.5ex]
  \centerline{{\small $f(x) = 2^x$}}
  \end{minipage}
  \begin{minipage}{.45\textwidth}
  \scalebox{.7}{
  \begin{tikzpicture}[default,baseline=0cm]
    \diagram{-2.5}{2.5}{-1}{4}{1}
    \diagramannotatez
    \diagramannotatexx{-1,1}
    \diagramannotatey{1}
    \begin{scope}[ultra thick]
    \draw[cgreen] plot[smooth,domain=-2:2.5,samples=300] (\x,{.5^\x});
    \end{scope}
  \end{tikzpicture}
  }\\[.5ex]
  \centerline{{\small $f(x) = 0.5^x$}}
  \end{minipage}
  \end{center}
  \pause 
  \vspace{-1ex}
  
  \begin{alertblock}{}
  These functions are called exponential since the
  variable $x$ is in the exponent. Do not confuse them with
  power functions $x^a$!
  \end{alertblock}
\end{frame}