How to LU facctorisation of a 4 by 4 matrice using gaussian eilimination! I have a 4 by 4 matrice,
A = [2 -2 0 0]
    [2 -4 2 0]
    [0 -2 4 -2]
    [0 0 2 -4]
How would I use Gaussian Elimination to find the LU factorisation of the matrix
Please could someone explain how to do this!? I have an exam where a similar question will come up so i really want to be able to fully understand this. I can do and completely understand Gaussian elimination of a 3 by 3 matrix but not when it is not a system on equations! I havnt seen anything like this before!
Many thanks

Here's your matrix $A$, and you multiply it on the left with a 4 by 4 Identity matrix (it's always going to be the same dimensions as your $A$ matrix). So it'll look like $[I]*[A]$, and then you do Gaussian Elimination (GE) to your $A$ matrix, and make sure you keep track of your row operations that you do. Ex that's not important to your question: 
$$\
r_{2} = r_{2} - 2r_{1}$$
When you apply it to your Identity matrix, make sure you change it to:
$$\
c_{1} = c_{1} + 2c_{2}$$
Where you then apply it as a column operation to the identity matrix. You keep doing those same steps until you end with your lower triangular matrix ($L$) on the left, and an upper triangular matrix on the right ($U$). Then $A = LU$. I will post an actual example soon.
Note: If you have to switch rows, then you have to multiply by a Permutation matrix, P. The steps you would do it would be PAx = Pb. I will write out an example, and somehow figure out how to post it here.
