Graphing Horizontal and Vertical Lines
If the coefficient of a variable in a linear equation is 0, then that
variable is usually omitted from the equation. For example, the equation y = 0
Â· x + 2 is written as y = 2. Because x is
multiplied by 0, any value of x can be used as long as y is 2. Because the ycoordinates
are all the same, the graph is a horizontal line.
Example 1
Graphing a horizontal line
Graph y = 2. Plot at least four points.
Solution
The following table gives four points that satisfy y = 2, or y = 0
Â· x + 2. Note that it is easy to determine y
in this case because y is always 2.
x 
2 
1 
0 
1 
y = 0 Â· x + 2 
2 
2 
2 
2 
The horizontal line through these points is shown in the figure below.
If the coefficient of y is 0 in a linear equation, then the graph is a
vertical line.
Example 2
Graphing a vertical line
Graph x = 4. Plot at least four points.
Solution
We can think of the equation x = 4 as x = 4 + 0
Â· y. Because y is multiplied by 0, the equation is satisfied by any
ordered pair with an xcoordinate of 4.
x = 4 + 0 Â· y 
4 
4 
4 
4 
y 
2 
1 
0 
1 
The vertical line through these points is shown in the figure below.
