The trace of the matrix A = 1 - 5 7 0 7 9 11 8 9 is

Given,

$A=\left[\begin{array}{ccc}1& -5& 7\\ 0& 7& 9\\ 11& 8& 9\end{array}\right].$ 

To find : trace of matrix

Now,

We know that,

 Trace of matrix $tr\left(A\right)=$sum of diagonal elements.

$\Rightarrow tr\left(A\right)=a_{11}+a_{22}+a_{33}$

$\Rightarrow tr\left(A\right)=1+7+9=17.$

Hence, trace of matrix is $17$.