Let $A=\left[\begin{array}{ccc}4 & -2 & 8 \\ 3 & 8 & -7\end{array}\right]$ and $\operatorname{det}(\mathrm{A}-\alpha \mathrm{I})=0$, where $\alpha$ is a real number. If the largest possible value of $\alpha$ is p , then the circle $(x-\mathrm{p})^2+(y-2 \mathrm{p})^2=320$, intersects the co-ordinate axes at