Upper triangular need to be interpreted as getting only zero entries under the most crucial diagonal, which starts in the upper left corner. Illustration[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://spanking-knickers68.blogerus.com/17967001/helping-the-others-realize-the-advantages-of-how-t-u-an-l-b-d