Answer: y = −2.
- A y = 2
- B y = −2
- C x = −2
- D y = −8
Correct answer: B. y = −2
Explanation: For x² = 4ay with 4a = 8, a = 2, so the directrix is y = −2.
All four conics form a single family distinguished only by eccentricity: a circle is the most "closed" (e=0), an ellipse is an elongated closed curve, a parabola is the borderline open curve (e=1), and a hyperbola has two separate open branches (e>1).
Concept context
Study circles, parabolas, ellipses, and hyperbolas as curves formed by intersecting a plane with a double cone, with their standard equations and key properties.