Q. The equation of the directrix of the parabola $x^{2} + 8y - 2x = 7$ is
A) $y = 3$
B) $y = - 3$
C) $y = 2$
D) $y = 0$
Explanation
(a)
Given equation can be rewritten as
$(x - 1)^{2} = - 4 \times (2)(y - 1)$
$\Rightarrow \ \ \ \ \ X^{2} = - 4aY$, where$\ X = x - 1,\ Y = y - 1$
So, equation of directrix is
$Y = a$
$\Rightarrow \ \ y - 1 = 2 \Rightarrow \ y = 3$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.