where T, is invertible and T2 is nilpotent. If T, is the product of three positive matrices, then T is the product of three nonnegative matrices. Proof. We may assume that T2 is upper triangular. Let m and n be the sizes of T, and T, respectively. We prove our assertion by induction on nstarting with n = m. If n = m, that is, T = T,, then this is trivially true. Assume that the
assertion holds for n - 1 ( > m). Let T’ be the matrix obtained from T by deleting its last row and column. We have