Explain why 3x^2+kx-1 is never always positive for any value of k

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