deletions | additions       diff --git a/untitled.tex b/untitled.tex  index ec1c01c..39fcf88 100644  --- a/untitled.tex  +++ b/untitled.tex 
...
\begin{vmatrix} a_{12} & a_{11} \\ a_{32} & a_{31}\end{vmatrix} &  \begin{vmatrix} a_{11} & a_{12} \\ a_{21} & a_{22}\end{vmatrix}   \end{bmatrix}  \end{equation} If we define an operation that is $RCR_ij(A):=R_{ij}$, remove column, row $ij$ on $A$, then this is expressible as  A^{-1}=\begin{bmatrix}   a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33}  \end{bmatrix}