Question

Find the minors of elements of second row of determinant $\left|\begin{array}{ccc}2& 3& 4\\ 3& 6& 5\\ 1& 8& 9\end{array}\right|$.

Answer 1

$A=\left|\begin{array}{ccc}2& 3& 4\\ 3& 6& 5\\ 1& 8& 9\end{array}\right|=0$
Minor of $a_{21}(=3)$ $A_{21}=\left|\begin{array}{cc}3& 4\\ 8& 9\end{array}\right|=27-32=5$
Minor of $a_{22}(=6)$ $A_{22}=\left|\begin{array}{cc}2& 4\\ 1& 9\end{array}\right|=18-4=14$
Minor of $a_{23}(=5)$ $A_{23}=\left|\begin{array}{cc}2& 3\\ 1& 8\end{array}\right|=16-3=13$