A parabola has a vertex at the origin. The equation of the directrix of the parabola is y is equal to 3 What are the coordinates of its focus?

The directrix is the horizontal line y = 3, so the parabola’s axis is vertical. The vertex lies halfway between the focus and directrix along that axis. Since the vertex is at (0, 0), the focus must be 3 units on the opposite side of the vertex from the directrix: (0, −3). Thus, choice B is correct.

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