The parabola has a focus at (−3, 0) and directrix x = 3. What is the correct equation for the parabola?

The focus and directrix lie on the horizontal line y = 0, so the parabola opens left or right. Its vertex is halfway between the focus (−3, 0) and directrix x = 3, giving vertex (0, 0). The focus is 3 units left of the vertex, so p = −3; using the horizontal-parabola form y² = 4px gives y² = 4(−3)x = −12x, which is choice D.

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