Discussion Forum

If  $A=\begin{bmatrix}3 & 4 \\5 & 7 \end{bmatrix}$ , then A , (adj A) is equal to

Answer:

Explanation:

$A=\begin{bmatrix}3 & 4 \\5 & 7 \end{bmatrix}$

 |A|=21-20=1

$\therefore$   $A(adj A)=\begin{bmatrix}3 & 4 \\5 & 7 \end{bmatrix}\begin{bmatrix}7 & -4 \\-5 & 3 \end{bmatrix}$

 =$\begin{bmatrix}1 & 0 \\0 & 1 \end{bmatrix}=1.\begin{bmatrix}1 & 0 \\0 & 1 \end{bmatrix}=|A|.1$