Answer: 4/5.
- A 3/5
- B 4/5
- C 5/4
- D 9/25
Correct answer: B. 4/5
Explanation: a2=25, b2=9, so c2 = 25-9 = 16, c=4. Eccentricity e = c/a = 4/5.
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.