您可以使用\overbrace
和\underbrace
:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\overbrace{a}^{\text{output}} = \underbrace{b}_{\text{significant}} + \underbrace{c + d}_{\text{non significant}}
\end{equation}
\end{document}