SOLUTION: an n *n matrix A is called nilpotent if, for some positive integer k, A^k = o, where o is the n*n zero matrix. Prove that id A is nilpotent, the det A = 0.
For any matrix A, = .
If A is a nilpotent matrix, then = 0; hence = 0.
It implies that for nilpotent matrix A = 0 for some integer k > 0; hence, det(A) = 0. QED