Question

The cofactors of elements in second row of the determinant $\left|\begin{array}{ccc}2& -1& 4\\ 4& 2& -3\\ 1& 1& 2\end{array}\right|$ are

• A. $5,6,4$
• B. $6,0,-3$
• C. $5,1,8$
• D. $6,0,3$

Answer 1

The correct option is B $6,0,-3$

$\left|\begin{array}{ccc}2& -1& 4\\ 4& 2& -3\\ 1& 1& 2\end{array}\right|C_{21}=-\left|\begin{array}{cc}-1& 4\\ 1& 2\end{array}\right|=6C_{22}=\left|\begin{array}{cc}2& 4\\ 1& 2\end{array}\right|=0C_{23}=-\left|\begin{array}{cc}2& -1\\ 1& 1\end{array}\right|=-3$