Q. The directrix of the parabola $x^{2} - 4x - 8y + 12 = 0$ is
A) $y = 0$
B) $x = 1$
C) $y = - 1$
D) $x = - 1$
Explanation
(c)
Given equation can be rewritten as
$(x - 2)^{2} = 8(y - 1)$
$\Rightarrow \ X^{2} = 4AY\$
Where $X = x - 2,\ Y = y - 1$ and $A = 2$
So, directrix is given by
$Y = - A\ \Rightarrow \ \ y - 1 = - 2$
$\Rightarrow \ y = - 1$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.