Mein LaTeX-Forum

\documentclass[8pt]{beamer}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage{graphicx}
\usetheme{Madrid}
\begin{document}
\begin{frame}[t]
\begin{align*}
A=&\overbrace{A_1+...+A_n}^{\text{Lauter A's}}\\
&\updownarrow \hspace{1.25cm} \updownarrow \\
&\underbrace{B_1 \ \ \ \,\,  ... \ \ \ \,  B_n}_{\text{Lauter B's}}
\end{align*}
\end{frame}
\end{document}
 

\documentclass[8pt]{beamer}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage{hf-tikz}

\usetheme{Madrid}

\begin{document}
\begin{frame}[t]
\begin{align*}
A=&\overbrace{A_1+\ldots+A_n}^{\text{Lauter A's}}\\
&\updownarrow \hspace{1.25cm} \updownarrow \\
&\underbrace{B_1 \ \ \ \,\,  \ldots \ \ \ \,  B_n}_{\text{Lauter B's}}
\end{align*}

{\renewcommand{\arraystretch}{1.4}
\begin{align*}
\tikzmarkin{a}A=&\underbrace{\overbrace{%
\begin{array}[t]{@{}c@{\,}c@{\,}c@{}}
A_1          & +\ldots+ & A_n\tikzmarkend{a}\\
\updownarrow &          & \updownarrow\\
B_1          & \ldots   & B_n
\end{array}}^{\text{Lauter A's}}}_{\text{Lauter B's}}
\end{align*}}
\end{frame}
\end{document}

\documentclass[8pt]{beamer}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage[customcolors, beamer]{hf-tikz}

\usetheme{Madrid}
\hfsetfillcolor{blue!10}
\hfsetbordercolor{blue}

\begin{document}
\begin{frame}[t]
\begin{align*}
A=&\overbrace{A_1+\ldots+A_n}^{\text{Lauter A's}}\\
&\updownarrow \hspace{1.25cm} \updownarrow \\
&\underbrace{B_1 \ \ \ \,\,  \ldots \ \ \ \,  B_n}_{\text{Lauter B's}}
\end{align*}

{\renewcommand{\arraystretch}{1.4}
\begin{align*}
\tikzmarkin<2>{c}A=&\underbrace{\overbrace{%
\begin{array}[t]{@{}c@{\,}c@{\,}c@{}}
A_1          & +\ldots+ & A_n\tikzmarkend{c}\\
\updownarrow &          & \updownarrow\\
B_1          & \ldots   & B_n
\end{array}}^{\text{Lauter A's}}}_{\text{Lauter B's}}
\end{align*}}
\end{frame}
\end{document}