Problem:
Compute the trace of
$\left(
\begin{array}{cccc}
 7 & -9 & -9 & -3 \\
 7 & 4 & 9 & 3 \\
 0 & 6 & 2 & 6 \\
 -9 & 1 & -4 & 3 \\
\end{array}
\right)$.
Answer:
$16$
{'source': 'AMPS', 'file': 'amps/mathematica/linear_algebra/trace/38454.txt'}