Horizontal and Vertical Lines
Any equation of the form x¼a, where a is a real number, is the graph of a
vertical line passing through the point (a, 0) on the x axis.
EXAMPLE
Graph the line x¼5.
SOLUTION
Draw a vertical line passing through the point (5, 0) on the x axis (see Fig.
11-14).
Any equation of the form y¼b, where b is any real number, is the graph
of a horizontal line passing through the point (0, b) on the y axis.
EXAMPLE
Graph the line y¼4.
SOLUTION
Draw a horizontal line through the point (0, 4) on the y axis (see Fig. 11-15).
CHAPTER 11 Graphing 215
Fig. 11-14.