Determine the value of kkk so the parabola y=x2−kx+4y = x^2 - kx + 4y=x2−kx+4 is tangent to the x-axis.
k=2k = 2k=2
k=±4k = \pm 4k=±4
k=−4k = -4k=−4
k=4k = 4k=4