Upper triangular should be interpreted as obtaining only zero entries below the key diagonal, which commences for the higher remaining corner. Case in point[edit] If a square, invertible matrix has an LDU (factorization with all diagonal entries of L and U equivalent to 1), then the factorization is exclusive.[5] http://lorenzoqgxpb.blogstival.com/17839544/a-review-of-how-t-u-an-l-b-d