What is the eccentricity of the ellipse x^2 / 25 + y^2 / 16 = 1? (Hard)
Answer and explanation
Correct answer: B. 3/5
- Step 1: Here a^2 = 25 and b^2 = 16. Eccentricity formula is e = sqrt(1 - b^2 / a^2). Step 2. e = sqrt(1 - 16/25) = sqrt(9/25) = 3/5. Answer: 3/5. Why not the others: 4/5 is the ratio of semi-minor to semi-major axis b/a; 9/25 is e^2; 5/3 is the inverse ratio a/e.
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