Question

与圆x²+y²-4x＝0外切，又与y轴相切的圆的圆心轨迹方程是

1. A.
   y²＝8x
2. B.
   y²＝8x(x＞0)和y＝0
3. C.
   y²＝8x(x＞0)
4. D.
   y²＝8x(x＞0)和y＝0(y＜0)

Answer 1

D