# Lesson 9Turn It AroundPractice Understanding

Use the distance formula to find . Leave in radical form.

## Set

The focus, , and the equation of the directrix are given. The coordinates for points and are also given. Make a sketch of the given information. Then use the diagram and the distance formula to prove that points and lie on the same parabola.

• focus:

• directrix:

• : :

• focus:

• directrix:

• : :

• focus:

• directrix:

• : :

• focus:

• directrix:

• : :

## Go

Use the given information to write the equation of the circle.