Q. The equation of the directrix of parabola $y^{2} + 4y + 4x + 2 = 0$ is
A) $x = - 1$
B) $x = 1$
C) $x = - \frac{3}{2}$
D) $x = \frac{3}{2}$
Explanation
(d)
The equation of parabola can be written as
$(y + 2)^{2} = - 4\ \left( x - \frac{1}{2} \right)$
$\Rightarrow \ \ \ \ Y^{2} = - 4X$ where$\ X = x - \frac{1}{2},\ Y = y + 2\$
An equation of its directrix is $X = 1$
$\therefore$ Required directrix is $x = \frac{3}{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.