Website
National Council of Teachers of Mathematics

The Math Forum: Ask Dr. Math: Parabola

For Students 9th - 10th Standards
Dr. Math, in a reply to a student's question, explains how to find the location of the vertex and focus, calculate the distance between the focus and vertex, as well as identify the axis of symmetry and the directix.
Activity
Varsity Tutors

Varsity Tutors: Hotmath: Algebra Review: Axis of Symmetry of a Parabola

For Students 9th - 10th
Find a quick, concise explanation of the Axis of Symmetry of a Parabola. An example is given to help you understand how to find the axis of symmetry of a parabola.
Handout
Math Words

Math words.com: Axis of Symmetry of a Parabola

For Students 9th - 10th
A basic definition for what the axis of symmetry of a parabola is, along with an illustration.