Tony is trying to find the equation of a quadratic that has a focus of (–1, 4) and a directrix of y = 8. Describe to Tony your preferred method for deriving the equation. Make sure you use Tony's situation as a model to help him understand.
@Soniatonia

Question

Tony is trying to find the equation of a quadratic that has a focus of (–1, 4) and a directrix of y = 8. Describe to Tony your preferred method for deriving the equation. Make sure you use Tony's situation as a model to help him understand.
@Soniatonia

anonymous · Answer

Okay
Let's first start off with the vertex-form of a parabola, which is ^^ y = a(x-h)^2 + k

anonymous · Answer

Next we solve for the vertex of the quadratic by using the value of the focus and the directrix.

anonymous · Answer

Since we already know the focus is (-1, 4) and the direxrix is y=8, we will use the mid point formula from the focus to the directrix to find the y-value of the vertex.

anonymous · Answer

are you getting it so far?

marcon · Answer

kinda, a litttle

anonymous · Answer

Alright

anonymous · Answer

what don't you get?

marcon · Answer

just in general how to do it

anonymous · Answer

the x-value of the vertex will be the same as the x-value in the focus, -1

anonymous · Answer

Basically we have the values of the vertex, (h, k). plug those into the equation.

anonymous · Answer

let me draw it out so it'll be easier

anonymous · Answer

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