MCQ
If $A=\left[\begin{array}{cc}1 & 2 \\ 2 & -1\end{array}\right]$, then $\operatorname{adj}(A)=$ ______
- A$\left[\begin{array}{ll}1 & -2 \\ 2 & -1\end{array}\right]$
- B$\left[\begin{array}{cc}-1 & 2 \\ 2 & 1\end{array}\right]$
- ✓$\left[\begin{array}{cc}-1 & -2 \\ -2 & 1\end{array}\right]$
- D$\left[\begin{array}{cc}1 & 2 \\ -2 & -1\end{array}\right]$