A == 11 1 1 24 8 1 2 139 9 27 1 4 4 16 64)

Calculate an LR decomposition of A using the Gaussian elimination method.
Proceed as follows:
(a) Determine the lower triangular matrices L(1), L(2) and L(3) such that:

L(3)- L(2)- L(1)- A = R
with an upper triangular matrix R.

(b) Determine the inverse L of the product L(3)-L(2)-L(1) to obtain the decomposition A = L-R
to obtain