答案1
\documentclass{article}
\usepackage{amsmath}
\usepackage{nicematrix}
\begin{document}
\begin{equation}
[\text{\bf M}]_\text{consistent}=\tfrac{SL}{420}
\begin{bNiceMatrix}[light-syntax]
156 22L 54 -13L;
22L 4L^2 13L -3L^2;
54 13L 156 -22L;
-13L -3L^2 -22L 4L^2
\end{bNiceMatrix}
\end{equation}
\end{document}