A=[2 3 -1; 1 2 4; -2 0 1]
det(A)
inv(A)
B=[A(2,:);A(1,:);A(3,:)]
det(B)
C=[A(1,:);2*A(2,:);A(3,:)]
det(C)
D=[A(1,:);A(2,:)+A(3,:);A(3,:)]
det(D)