Sasha and Keoni make sense of parameters that can change the vertex of a parabola on the coordinate grid. They also revisit what they already know about how the p-value changes the shape of the graph of the parabola.
Episode Supports
Focus Questions
For use in a classroom, pause the video and ask these questions:
1. [Pause video at 3:54]. What is happening to the directrix as the value of k changes?
2. [Pause video at 3:54]. What are the coordinates of the focus of the parabola in red?
Supporting Dialogue
Focus students’ attention on precision of language by attending to Sasha’s justification:
1. Sasha provides justification for why the directrix does not move when the vertex moves to (7,0) [6:18-6:24]. Can someone revoice her idea?
2. Can someone revoice Sasha’s idea using mathematical vocabulary? What about someone else? Is there another way to revoice her idea?
Math Extensions
1. Use the link to GeoGebra applet to explore how you can change the position of a parabola so that the p-value is still 3 and the vertex is at (–5, 0). What are the coordinates of the focus for this parabola? How do you know?
2. How can you adjust the p-value and the h-value to get a parabola with a vertex at (7,0) and a focus at (7, 2)? How do you know? Where is the p-value on the graph?
