I have to factor the matrix into the LU decomposition with the LU factorization algorithm with lii = 1 for all i.

A =

[2 -1 1]

[3 3 9]

[3 3 5]

U =

[2 -1 1]

[0 9/2 15/2]

[0 0 -4]

L =

[1 0 0]

[1.5 1 0]

[1.5 1 1]

I know how to get U from just row reducing but I don't get how L is found.