helpful.
Another way of doing it is provided by Paul Blaga:

\documentclass{beamer}
\begin{document}
\begin{frame}
\begin{overprint}
\only<1>{
\[
f(x) = k \cdot e^{-x/3}
\]
}
\only<2>{\[ f(x) = \frac{1}{3}\cdot e^{-x/3} \]}
\end{overprint}
\end{frame}
\begin{frame}
\begin{overlayarea}{\textwidth}{3cm}
\only<1>{
\[
f(x) = k \cdot e^{-x/3}
\]
}
\only<2>{\[ f(x) =\frac{1}{3}\cdot e^{-x/3} \]}
\end{overlayarea}
\end{frame}
\end{document}

The above question was answered by **Thomas E. Price**,
and **Paul Blaga**, , a
member of the editorial board of this journal.

**Q:** Dear Nelly: In my latest book, I start each chapter
with a quotation. Now one of those quotations is in ancient Greek.
How do I typeset that in LaTeX, including all the accents?

**A:** This is actually not all that difficult to achieve. All
we need is the Babel package. Include it in the preamble like this:

\usepackage[greek,english]{babel}
\languageattribute{greek}{polutoniko}

This loads Babel with English as the default language, but also
with support for Greek. Setting the `polutoniko` attribute
enables the support for multiple accents. Modern Greek does not
use those, but ancient Greek does.
Now one can include a Greek quotation like this:

\begin{quotation}
\selectlanguage{polutonikogreek}
>akr~atos diqogwmon'ew p'anteqnos anafor`es pr`os ~>wrai >'wra.
\end{quotation}

Note the use of > for spiritus lenis, < for spiritus asper, and `, '
and ~ for the regular accents. The correspondence between our own
alphabet and the Greek, as used by LaTeX, is quite straightforward.
The easiest way to get an overview of the correspondence between
your keyboard and the Greek letters is to just print off the
alphabet:
\selectlanguage{polutonikogreek}
abcdefghijklmnopqrstuvwxyz
ABCDEFGHIJKLMNOPQRSTUVWXYZ

The above question was answered by **Yuri Robbers**, a
member of the editorial board of this journal. He can be
reached at