Question

If $A=\left[\begin{array}{cc}3& -5\\ -1& 0\end{array}\right]$, then adj. $A$ is equal to

• A. $\left[\begin{array}{cc}3& 5\\ 1& 0\end{array}\right]$
• B. $\left[\begin{array}{cc}0& -5\\ -1& 3\end{array}\right]$
• C. $\left[\begin{array}{cc}0& 5\\ 1& 3\end{array}\right]$
• D. $\left[\begin{array}{cc}0& -1\\ -5& 3\end{array}\right]$

Answer 1

The correct option is C $\left[\begin{array}{cc}0& 5\\ 1& 3\end{array}\right]$

co-factor of $A_{11}=0$; co-factor of $A_{12}=5$; co-factor of $A_{21}=1$; co-factor of $A_{22}=3$
$adjA=\left[\begin{array}{cc}0& 5\\ 1& 3\end{array}\right]$
Ans: C