with(linalg): A1:=matrix([[1,-3,2,6], [1,4,-1,4], [5,6,1,20]]); A2:=addrow(A1,1,2,-1); A3:=addrow(A2,1,3,-5); A4:=mulrow(A3,2,1/7); A5:=addrow(A4,2,3,-21); swaprow(A5,1,2);