Derive the equation of the parabola with a focus at (2, 4) and a directrix of y = 8.

Question

brynndelyn · Answer

Can you explain what a directrix is?

brynndelyn · Answer

Lol wut?

brynndelyn · Answer

None of this makes any sense to me...

xapproachesinfinity · Answer

|dw:1430877421249:dw|

xapproachesinfinity · Answer

the directrex is the line that is at same distance to vertex and vertex to focus

brynndelyn · Answer

I still don't really understand

brynndelyn · Answer

Sorry for being slow

xapproachesinfinity · Answer

perhaps drawing the point (2,4) and the line y=8 will make more sense
to you so let's do that

zepdrix · Answer

|dw:1430877495469:dw|Here is another cool thing about parabolas :)
If you chose any point on the parabola,
the `distance between the focus and the point`
will always be equal to
the `distance between the point and the directrix`.

I've drawn a couple of examples here to illustrate.
Just something to keep in mind :)