If \( A = \begin{vmatrix} 4 & k & k \\ 0 & k & k \\ 0 & 0 & k \end{vmatrix} \) and \( \det(A) = 256 \), then \( |k| \) equals:
Show Hint
When you see a matrix with a "triangle" of zeros, don't expand it manually. Just multiply the diagonal entries. It works for both \( \text{det}(A) \) and finding eigenvalues.