I see, thanks! Here, I finally got it: (%i19) M:matrix([1,2],[3,4]); [ 1 2 ] (%o19) [ ] [ 3 4 ] (%i20) get_lu_factors( lu_factor(M) ); [ 1 0 ] [ 1 0 ] [ 1 2 ] (%o20) [[ ], [ ], [ ]] [ 0 1 ] [ 3 1 ] [ 0 - 2 ] (%i21) -- Dotan Cohen http://what-is-what.com http://gibberish.co.il