Question

The equation of the directrix of the parabola $y^2+4y+4x+2=0$ is

• A. $x=-1$
• B. $x=1$
• C. $x=-3/2$
• D. $x=3/2$

Answer 1

Answer: (D)

We can write the equation of the given parabola as ${\left(y+2\right)}^2=-4\left(x-\frac{1}{2}\right)$
Shifting the origin $(1/2,-2)$, the equation of parabola becomes $Y^2=-4X$, where $X=x-1/2$, $Y-y+2$.
The equation of its directrix is $X=1$.
Hence, required equation of directrix is $x-\frac{1}{2}=1$ or $x=3/2$.