Hi

Im confused on where to start in proving this question

Let A = $\displaystyle \left(\begin{array}{cc}a&b\\c&d\end{array}\right)$ where a, b, c and d are real numbers. Show that the characteristic equation of A is $\displaystyle \lambda^2 - tr(A)\lambda + det(A) = 0$

where tr(A) = trace of A.

Thanks