What is the condition on kkk for which the line y=x+ky = x + ky=x+k is a tangent to the circle x2+y2=4x^2 + y^2 = 4x2+y2=4?
k=±2k = \pm 2k=±2
k=±22k = \pm 2\sqrt{2}k=±22
k=±1k = \pm 1k=±1
k=±4k = \pm 4k=±4