答案1
尝试
\documentclass{beamer}
\usetheme{malmoe}
\begin{document}
\begin{frame}{Test}
\begin{equation}
\begin{split}
E_{t-1}[r_{i,t}] = &\,\phi_{i,t-1}\,\lambda_{t-1}\,cov_{t-1}[r_{i,t},r_{w,t}]\,+\\
&(1 - \phi_{i,t-1})\,\lambda_{i,t-1}\,var_{t-1}[r_{i,t}]
\end{split}
\end{equation}
\end{frame}
\end{document}