Question:
If $A=\left(\begin{array}{cc}2 & -1 \\ 1 & 3\end{array}\right)$, then $A^{-1}=?$
A. $\left(\begin{array}{ll}\frac{3}{7} & \frac{-1}{7} \\ \frac{1}{7} & \frac{2}{7}\end{array}\right)$
B. $\left(\begin{array}{cc}\frac{3}{7} & \frac{1}{7} \\ \frac{-1}{7} & \frac{2}{7}\end{array}\right)$
c. $\left(\begin{array}{ll}\frac{1}{3} & \frac{1}{7} \\ \frac{1}{7} & \frac{2}{7}\end{array}\right)$
D.None of these
Solution:
