Discussion Forum

1)

 The cofactors of the elements of the first column of the matrix 

$A=\begin{bmatrix}2 & 0 &-1\\3 & 1&2\\ -1 &1 & 2 \end{bmatrix}$  are

Answer:

Option D

Explanation:

 Given matrix  

$A=\begin{bmatrix}2 & 0 &-1\\3 & 1&2\\ -1 &1 & 2 \end{bmatrix}$

 cofactor of the elements of first column of the matrix

$A_{11}=\begin{bmatrix}1 & 2 \\1 &2 \end{bmatrix}=2-2=0$

$A_{21}=-\begin{bmatrix}0 & -1 \\1 &2 \end{bmatrix}=-(0+1)=-1$

$A_{31}=\begin{bmatrix}0 & -1 \\1 &2 \end{bmatrix}=0+1=1$

 $\therefore$   cofactor is (0,-1,1)