Houghton Mifflin Harcourt
Harcourt: School Publishers: Negative Slope
This site provides an example of a negative slope, including the equation of the line shown. Also given is a definition of a negative slope.
Texas A&M University
Wtamu Virtual Math Lab: Intermediate Algebra: The Slope of a Line
This tutorial will show you how to find a the slope of graph, write a linear equation in slope-intercept form. You'll also learn how to determine whether two lines are parallel or perpendicular to each other. For advanced math students.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: When Is a Slope 0 or Undefined?
At this site Dr. Math gives a discussion on the slopes of lines. The Dr. gives an analogy between the slope of a line and walking up and down hills. The Dr. explores the concept of undefined and zero slopes through his response to a...