Multiplication of two determinats
let A=\[\begin{vmatrix}a_{11}&a_{12}\\a_{21}&a_{22}\end{vmatrix}\] and B=\[\begin{vmatrix}b_{11}&b_{12}\\b_{21}&b_{22}\end{vmatrix}\]
Then the product AB=\[\begin{vmatrix}a_{11}b_{11}+a_{12}b_{21}&a_{11}b_{12}+a_{12}b_{22}\\a_{21}b_{11}+a_{22}b_{21}&a_{21}b_{12}+a_{22}b_{22}\end{vmatrix}\]
Example \[\begin{vmatrix}2&3\\1&0\end{vmatrix}\]\[\begin{vmatrix}5&1\\1&2\end{vmatrix}\]=-27
