Do lines w/ the slope of 0 or undefined have an equation?
Recall that the slope of a line is defined as the rise/run. So if it has a slope of 0 the rise = 0 – that means it is a horizontal line. Horizontal lines have equations of the form y = c where c is any real number. For example y = 4. This graphs as a horizontal line because for any x you have, y will always have a value of 4. If the line has an undefined slope then the run = 0 (division by 0 is undefined) and the line is a vertical line. Vertical lines have equations of the form x = c where c is any real number. For example x = -2. All the x values MUST be -2 and the y value can be anything.
