Question

If $A=\left[\begin{array}{ccc}1& -5& 7\\ 0& 7& 9\\ 11& 8& 9\end{array}\right]$, then trace of matrix A is.

• A. $17$
• B. $25$
• C. $3$
• D. $12$

Answer 1

Answer: (A)

$17$

We know that, $tr\left(A\right)=\sum _{i=1}^n{a}_{ii}$
$\therefore$ If A$=\left|\begin{array}{ccc}1& -5& 7\\ 0& 7& 9\\ 11& 8& 9\end{array}\right|$, then
$tr\left(A\right)=1+7+9=17$

Hence, option A is correct.