Question

The cofactor of the element '4' in the determinant $\left|\begin{array}{cccc}1& 3& 5& 1\\ 2& 3& 4& 2\\ 8& 0& 1& 1\\ 0& 2& 1& 1\end{array}\right|$ is

• A. 4
• B. -10
• C. 10
• D. -4

Answer 1

The correct option is C 10

The cofactor of element 4, in the $2^{nd}$ row and $3^{rd}$ column is
$=(-1{)}^{2+3}\left|\begin{array}{ccc}1& 3& 1\\ 8& 0& 1\\ 0& 2& 1\end{array}\right|$ = - {1(-2)-3(8-0)+1.16}
=10.