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For the parabola 9x² - 24xy + 16y² - 20x - 15y - 60 = 0, let L be the distance between its focus and directrix. Find L.
- 3
- 1
- 2
- 4
Correct answer: 3
Solution
Writing (3x - 4y)² = 20x + 15y + 60 and reducing to standard parabolic form gives 4a = 6, so the focus-directrix distance 2a = 3.
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