Chelsea is trying to find the equation of a quadratic that has a focus of (1, 3) and a directrix of y = −3. Describe to Chelsea your preferred method for deriving the equation. Make sure you use Chelsea's situation as a model to help her understand.

Question

anonymous · Answer

@trevorttreesh

anonymous · Answer

http://hotmath.com/hotmath_help/topics/finding-the-equation-of-a-parabola-given-focus-and-directrix.html this might help you

anonymous · Answer

I have seen that but, I still dont understand it

anonymous · Answer

thats all i got on that one

anonymous · Answer

@tkhunny

anonymous · Answer

@austinharding @austinL

tkhunny · Answer

Start with the Vertex.  It is exactly between the focus and the vertex.

anonymous · Answer

So, -1?

tkhunny · Answer

No, not quite.  It should be the coordinates of a point.

Directrix of y = -3 indicates a vertical parabola.  It opens up or down.
Focus (1,3) now indicates three things:
1) Axis of symmetry is x = 1
2) Focus is (1,0)
3) Parabola opens UP.

anonymous · Answer

okay, so what would be the next step to this?

tkhunny · Answer

Have you a standard form of a parabola?  Usually (x-h)^2 = 4p(y-k) or something like that.  Find it and present it and we can fill in the pieces.