If $A=\left[\begin{array}{ll}3 & -5 \\ 4 & -7\end{array}\right]$, then $A^{-1}$ is: |
$\left[\begin{array}{ll}-7 & 5 \\ -4 & 3\end{array}\right]$ $\left[\begin{array}{cc}7 & 5 \\ 4 & -3\end{array}\right]$ $\left[\begin{array}{cc}-7 & -5 \\ -4 & 3\end{array}\right]$ $\left[\begin{array}{ll}7 & -5 \\ 4 & -3\end{array}\right]$ |
$\left[\begin{array}{ll}7 & -5 \\ 4 & -3\end{array}\right]$ |
The correct answer is Option (4) → $\left[\begin{array}{ll}7 & -5 \\ 4 & -3\end{array}\right]$ $A=\left[\begin{array}{ll}3 & -5 \\ 4 & -7\end{array}\right]$ $|A|=3(-7)-(-5)(4)=1$ $adj\,A=\left[\begin{array}{ll}-7 & 5 \\ -4 & 3\end{array}\right]$ So $A^{-1}=\frac{adj\,A}{|A|}=\left[\begin{array}{ll}-7 & 5 \\ -4 & 3\end{array}\right]$ |