If the trivial solution is the only solution of the system of equations x−ky+z=0,  kx+3y−kz=0, 3x+y−z=0. Then the set of all values of k is

The condition for a homogeneous system of equations to have only trivial solution is Δ≠0⇒1-k1k3-k31-1≠0⇒1-3+k+k-k+3k+1k-9≠0 ⇒2k2+2k-12≠0⇒k2+k−6≠0k≠{2,   −3}