National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Line Problems
This site answers many general questions about linear equations and their graphs. A student posed several questions to Dr. Math regarding lines and their equations. Question number 4 is about the equation of a horizontal line and Dr....
Varsity Tutors
Varsity Tutors: Hotmath: Algebra Review: Horizontal Lines
Find a quick, concise explanation of equations of horizontal lines. An example is given and clearly explained for equations of both horizontal and vertical lines.
Other
Math N Stuff: Horizontal Lines Constant Functions
This site gives information regarding horizontal lines. The site contains a graph and poses a question relating to the equation of the line on the graph. The correct answer may be clicked on with a short reason.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Equation of a Line Parallel to an Axis
Dr. Math gives a short discussion on how to find the equation of a line parallel to an axis (, parallel or horizontal.)
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...