CK-12 Foundation
Ck 12: Algebra: Vertical Line Test
[Free Registration/Login may be required to access all resource tools.] Learn how to determine whether or not a relation is a function.
Texas A&M University
Wtamu Virtual Math Lab: College Algebra: Graphing Lines
Complete this tutorial to learn how to graph a straight line if given the y-intercept and slope and how to graph horizontal and vertical lines. View examples of lines with different slopes, and practice working with slope-intercept form.
Windstream
Ojk's Precalculus Study Page: Reflections and Symmetry
An introduction to the various types of symmetries that can occur in the graphs of functions. Uses vertical, horizontal, and oblique reflections as a means of recognizing symmetries.