The matrix124has one eigenvalue equal 30611p to 3. The

The matrix 1 2 4 has one eigenvalue equal
3 0 6
1 1 p

to 3. The sum of the other two eigenvalues is

Sum of the diagonal vector = sum of the Eigen values,
⇒ 1 + 0 + p = 3 + S
⇒ S = p – 2