1. This isn't really a specific question, but in general, what would be ways to find the vertex of a parabola? (Assuming you know all the necessary information and whatnot)


2. How do you find the directrix of a parabola, and what would be its use? 

 Mar 6, 2019

It depends what form your equation is in.


If it is of the form




Then the vertex is  (h,k) 

the focal length is |a|

If a is positive then it is concave up, if a is negative then it is concave down.

The focus is (h,k+a)  the axis of symmetry is x=h   and the directrix is   y=k-a


The definition of a parabola is the locus of all points equidistant from a line called the directrix and a point called the focus.

Give the directrix and the focus you can determine the equation of the parabola using locus (which is a fun things to do when you get used to the method)


What would you use the directrix for ? ... not sure what this question is after but if you google it the answer may become clear :/

 Mar 6, 2019

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