Engineering Board Exam Reviewer · Conic Sections and Transformation of Axes · hard
A conic has a focus at (2,0), the directrix x=8, and eccentricity 12. Find its equation.
- x216 + y24 = 1
- x212 + y216 = 1
- x216 - y212 = 1
- x216 + y212 = 1
Answer
D. x216 + y212 = 1
Solution
sqrt((x-2)2+y2)= 12|x-8| 4≤ft[(x-2)2+y2 ]=(x-8)2 3x2+4y2=48, i.e. x2/16+y2/12=1.
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