A given line called the directrix and a point called the focus determine a parabola. Here is one way to construct the curve.

Use a right triangle ABC (or a stiff piece of rectangular cardboard).

Place one leg of the triangle on the given line d. Fasten one end of a string with length BC at the given point F and the other end to the triangle at point B.

Put the tip of a pencil at point P and keep the string tight. The distance, FP + PB = BC.

As you move the triangle along line d, the point of the pencil will trace out a parabola.

Directions: Draw the parabola determined by line d and point F.

Use your drawings to complete this conclusion.

The greater the distance of point F from line d, _______________________________