What is the condition on kkk such that y=2x+ky = 2x + ky=2x+k is tangent to the ellipse x2+4y2=4x^2 + 4y^2 = 4x2+4y2=4?
k=±17k = \pm \sqrt{17}k=±17
k=±5k = \pm \sqrt{5}k=±5
k=±4k = \pm 4k=±4
k=±2k = \pm 2k=±2