If you haven't had calculus, then we do it this way:
A line is tangent to a parabola if and only if the assumption of their
equations holding true leads to a single solution with multiplicity 2.
We substitute (kx-3) for y in
This will have a single solution with multiplicity 2 if its discriminant
equals 0.
Those are the two and the only such values of k.
Edwin
