I would like to know how to add dash lines in Matrix (see figuge)
Cheers
S.L.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{bmatrix}
N & B_i \\
B_i^T & 0
\end{bmatrix}
\begin{bmatrix}
x_i\\
k
\end{bmatrix}
=\begin{bmatrix}
n\\
0
\end{bmatrix}
\text{ with } n = A^TPl
\end{equation}
\end{document}
