Express the Eigenvalues of a 2 by 2 Matrix in Terms of the Trace and Determinant
Problem 631
Let $A=\begin{bmatrix}
a & b\\
c& d
\end{bmatrix}$ be an $2\times 2$ matrix.
Express the eigenvalues of $A$ in terms of the trace and the determinant of $A$.
Add to solve later 
