Lawrence Hall of Science
The Math Page: Skill in Algebra: The Slope of a Straight Line
Here is a site that clearly and thoroughly explains many topics surrounding the slope of a line, including slope of horizontal, vertical, parallel, and perpendicular lines in addition to the formula and concept of slope. There are...
Math Planet
Math Planet: Parallel and Perpendicular Lines
Provides examples and a video lesson that illustrates parallel and perpendicular lines.
Texas A&M University
Wtamu Virtual Math Lab: Beginning Algebra: Slope
A tutorial on slope with many step-by-step examples. The tutorial clarifies what slope is, how to find slope between two points on a graph, and how slopes of parallel and perpendicular lines are related.
University of Regina (Canada)
University of Regina: Math Central: Characteristics of a Line
Characteristics of a line are explained to learners through four different lessons. Topics include intercepts, slope, and special line cases. The lessons have an overview, materials, procedures, and evaluation techniques.
Varsity Tutors
Varsity Tutors: Hotmath: Slope of a Line
Twenty-two problems present a practice finding the slope of a line. The solutions are only available with a paid subscription.
University of Regina (Canada)
University of Regina: Math Central: Characteristics of a Line
Characteristics of a line are explained to students through four different lessons. Topics include intercepts, slope, and special line cases. The lessons have an overview, materials, procedures, and evaluation techniques.
Khan Academy
Khan Academy: Parallel & Perpendicular Lines From Equation
Use your knowledge about the slopes of parallel and perpendicular lines to solve some problems. For example, what's the equation of the lineperpendicular to y=3x-3 and passes through the point (-8, -2).