Question

derive the equation of the parabola with a focus at (0.4) and a directix of y = 4

Answer 1

@Hero Heyyy! . Are you familiar with this?

Answer 2

@hartnn Hey are you familiar with this?

Answer 3

the focus is at x=0, y=4 and the directrix is y=4?

Answer 4

Yes correct (0,4)

Answer 5

@DemolisionWolf

Answer 6

this one is confusing for me, i'm not sure what to do when the directrix and focus have the same y-value. as far as i can figure, it's not a parabola, but it's a line...

Answer 7

@agent0smith

Answer 8

@terenzreignz

Answer 9

Ugh ...math..

Answer 10

Ive looked at help videos and i got so lost

Answer 11

there are 3 equations that relate focus and diretrix to the equation of a parabola

Ax^2+Bx+c

focus
x=-B/(2A)
y=c-(b^2-1)/4a

directrix
y=c-(b^2+1)4a

..
but the two last equations will both equal 4, which is what i'm stuck at becuase one equation has a +1 in it while the other has a -1, so i'm not sure...

Answer 12

The one I learned was 1/4(p) = a

Answer 13

and to find the focal length and vertex

Answer 14

1/4(p) = a this is a good eq. but if we plug in 0 for 'p' we get a= undefined.... so thats why I don't think it's a parabola, but it is a line

Answer 15

Im gonna call my teacher ...thanks :)

Answer 16

I'd guess it's a mistake.... you can't have the focus at the same spot as the directrix.

Is it (0, 4) for the focus? and a directix of y = 4? no negatives?

Answer 17

Yes @agent0smith