Theorem 4. Let A ∈ Cn×n be given. Then we can find matrices L, N ∈ Cn
with the following properties: (i) L + N = A
(ii) LN = N L
(iii) L is diagonalizable
(iv) N is nilpotent, i.e. N n = 0.
Moreover, the matrices L and N are unique (i.e. there exists only one pair of matrices with that property).