Q. The equation of a directrix of the ellipse $\frac{x^{2}}{16} + \frac{y^{2}}{25} = 1$ is
A) $3y = \pm 5$
B) $y = \pm 5$
C) $3y = \pm 25$
D) $y = \pm 3$
Explanation
(c)
Here, $a = 4,\ b = 5$ and $e = \sqrt{1 - \frac{16}{25}} = \frac{3}{5}$
$\therefore$ Equation of directrix is$\ y = \pm \left( \frac{5}{3/5} \right)$
$\Rightarrow 3y = \pm 25$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.