Question

How do I find the directrix and focal length of a parabola? For example, y=1/12x^2

Answer 1

any point on a parabola is equidistant to the focus and the directrix

Answer 2

But how do I find the directrix...?

Answer 3

there is probably a formula

Answer 4

Ok, thanks.

Answer 5

i believe the form is properly: 4py =x^2

Answer 6

Oh, it is D:?

Answer 7

y = 4x^2 has a focal point at (0, 1/16)

if we assume y=4px^2, that would make the focal point at (0,1) ...

Answer 8

Hm...that does seem to make sense. I put an example in my question. How would that work out?

Answer 9

y=1/12x^2 ; *12

12y = x^2

let 4p = 12 , p = 3 gives the distance we need from the vertex to find the focus and the directrix