Question

Equation of the directrix of the conic $x^2+4y+4=0$ is

• A. $y=1$
• B. $y=-1$
• C. $y=0$
• D. $x=0$
• E. $x=1$

Answer 1

Answer: (C)

Given equation can be rewritten as
$x^2=-4(y+1)$
$\Rightarrow$ $X^2=-4Y,$ where $X=x$ and $y=y+1$
Equation of directrix is $Y=1$
$\therefore$ $y+1=1$
$\Rightarrow$ $y=0$