hello :
(3x²+kx-1) is a quadratic polynome when : a =3 , b=k , c= -1
the discriminat Δ = b²-4ac ≥ 0 because ac = -3 < 0
-4ac >0 and b²≥0
the quadratic polynome has :2 solutios or 1 solution (Change of sign)
conclusion : is never always positive for any value of k
