Question:
If $A=\left(\begin{array}{ll}a & b \\ c & d\end{array}\right)$ then adj $A=?$
A. $\left(\begin{array}{cc}\mathrm{d} & -\mathrm{c} \\ -\mathrm{b} & \mathrm{a}\end{array}\right)$
B. $\left(\begin{array}{cc}-d & b \\ c & -a\end{array}\right)$
C. $\left(\begin{array}{cc}d & -b \\ -c & a\end{array}\right)$
D. $\left(\begin{array}{cc}-\mathrm{d} & -\mathrm{b} \\ \mathrm{c} & \mathrm{a}\end{array}\right)$
Solution:
