Question

What is the directrix of the parabola given by the equation x = -1/4 y^2?

Answer 1

write as
y^2=-4x
so comparing with
y^2=4ax
4a=4
a=1

since the vortex is at (0,0) so directrix should be at distance a from the vortex to the right..
x=1 should be directrix.