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A is a point on x²/25 + y²/9 = 1 and F1, F2 are the foci. The perimeter of triangle AF1F2 is
A18
B10
C16
D20
Answer & Solution
Correct answer: A. 18
AF1 + AF2 = 2a = 10 and F1F2 = 2c = 8, so the perimeter is 18.
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