Question

What are the eigen values of the followign $2\times 2$ matrix \($$\left[\begin{array}{cc}2& -1\\ -4& 5\end{array}\right]$$

• A. $-1,1$
• B. $1,6$
• C. $2,5$
• D. $4,-1$

Answer 1

The correct option is B $1,6$

${\lambda }_1+{\lambda }_2$ =\) Trace $\left(A\right)$ & ${\lambda }_1{\lambda }_2=|A|$
${\lambda }_1+{\lambda }_2=7$ & ${\lambda }_1{\lambda }_2=6$
${\lambda }_1=1$, ${\lambda }_2=6$