Illustrative Mathematics
Illustrative Mathematics: G Gpe Defining Parabolas Geometrically
The purpose of this task is to show that the points on a parabola can be characterized by being equidistant from a point (the focus) and a line (the directrix). Aligns with HSG-GPE.A.2.
Purple Math
Purplemath: Conics: Parabolas: Introduction
This reference material introduces the terms and equations related to parabolas in the context of conics. Also, relates concepts to previously-learned material and shows how to 'read' from the 'conics' form of the parabola equation.
Khan Academy
Khan Academy: Equation of a Parabola From Focus and Directrix
Given the focus and the directrix of a parabola, find its equation. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Windstream
Ojk's Precalculus Study Page: Parabolas
Good study tutorial about parabolas. There are examples of finding the equation of the parabola or the focal point and directrix that students can examine and attempt.