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10-71.

Using focus-directrix graph paper, sketch a parabola that has a horizontal directrix four units above the focus, which is at . You can get focus-directrix paper on the Lesson 10.1.3 Resource Page. 10-71 HW eTool (Desmos).

  1. Write an expression for the distance from the focus to any point on the parabola.

  2. Write an expression for the distance from the directrix to any point on the parabola.

    Notice that the closest point on the directrix is going to have the same -value.

  3. If all of the points on a parabola are equidistant from the focus and directrix, use your expressions from parts (a) and (b) to write an equation for the parabola.

Use this eTool to create a parabola.
Click the link at right for the full version of the eTool: INT2 10-71 HW eTool.