Question

The directrix of the parabola $x^2-4 x-8 y+12=0$, is

(A) $x=1$

(B) $y=0$

(C) $x=-1$

(D) $y=-1$

Answer 1

Given equation can be rewritten as

$(x-2)^2=8(y-1)$

$\Rightarrow X^2=8 Y$, this is a standard form of parabola.

On comparing with $X^2=4 a Y$, we get $a=2$

$\therefore$ Directrix is $Y=-a \Rightarrow y-1=-2 \Rightarrow y=-1$

So, The correct option will be (D).