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Mathematics 20 Online
OpenStudy (brynndelyn):

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

OpenStudy (brynndelyn):

Can you explain what a directrix is?

OpenStudy (brynndelyn):

Lol wut?

OpenStudy (brynndelyn):

None of this makes any sense to me...

OpenStudy (xapproachesinfinity):

|dw:1430877421249:dw|

OpenStudy (xapproachesinfinity):

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

OpenStudy (brynndelyn):

I still don't really understand

OpenStudy (brynndelyn):

Sorry for being slow

OpenStudy (xapproachesinfinity):

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

zepdrix (zepdrix):

|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 :)

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