Parabola Focus/Directrix Definition and Formula (Precalculus, Conic Sections, Lesson 2)

We learn that a parabola is the set of points for whom the distance to a line (the directrix) and a point (the focus) are equal. We then learn derive a formula for the parabola based on this definition.(x^2=4py)

Exposition: 0:00
Task 1: 2:01
Check 1: 2:44
Task 2: 3:24
Check 2: 4:23
Task 3: 5:41
Check 2: 6:10
Appendix #1 (Distance Formula): 8:32
Appendix #2 (Multiplying Expressions / "Expanding"): 10:44

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