Question

The cofactor of the element 4 in the determinant

$\left| \begin{matrix} 1 & 3 & 5 & 1 \\ 2 & 3 & 4 & 2 \\ 8 & 0 & 1 & 1 \\ 0 & 2 & 1 & 1 \end{matrix} \right|$ is

• A. 4
• B. 10
• C. –10
• D. –4

Answer 1

Answer: (B)

10

Answer 2

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