1.
Let A=[a35513234]A = \begin{bmatrix}a&3&5\\5&-1&3\\2&3&-4\end{bmatrix}, B=[b144c131d]B = \begin{bmatrix}b&1&4\\4&c&1\\-3&1&d\end{bmatrix}. tr(A)=4\text{tr}(A)=-4 and AB=[1017310252883]AB = \begin{bmatrix}-1&0&17\\-3&10&25\\28&-8&3\end{bmatrix}. Then a+b+c+d=a+b+c+d =