Question

If the traces of $A,B$ are $20$ and $-8$, then the trace of $A+B$ is:

• A. $12$
• B. $-12$
• C. $28$
• D. $-28$

Answer 1

The correct option is A $12$

the trace of an $n\times n$ square matrix A is defined to be the sum of the elements on the main diagonal (the diagonal from the upper left to the lower right) of A

the traces of A,B are 20 and −8, then the trace of $A+B$ is $trac(A+B)=trace\left(A\right)+trac\left(B\right)=20+-8=12$