Conic Sections Question 225
Question: The equations of the directrices of the ellipse $ 16x^{2}+25y^{2}=400 $ are
Options:
A) $ 2x=\pm 25 $
B) $ 5x=\pm 9 $
C) $ 3x=\pm 10 $
D) None of these
Show Answer
Answer:
Correct Answer: D
Solution:
$ \frac{x^{2}}{25}+\frac{y^{2}}{16}=1 $
therefore $ e=\sqrt{1-\frac{16}{25}}=\frac{3}{5} $ Therefore, directrices are $ x\pm \frac{5}{3/5}=0 $ or $ 3x\pm 25=0 $ .
BETA
