A=[0 1 2; 1 0 3; 4 -3 8]
inv(A)

A=[3 -7 -2 2 -9; 0 -2 -1 2 -4; 0 0 -1 1 5; 0 0 0 -1 1]
using RowEchelon
rref(A)

A=[2 4 -1 5 -2; -4 -5 3 -8 1; 2 -5 -4 1 8; -6 0 7 -3 1]
L,U = lu(A, Val{false})
L

U