Standard Form
Horizontal & Vertical Lines
If only one variable appears in the standard form, then the line will be either vertical or horizontal.
For example 3x = 9 is an equation in standard form with the y-term missing. Any value can be chosen for y, but the value of x will always be 3. The ordered pairs generated will have the form (3, y). Ordered pairs such as (3, -1), (3, 0), (3, 1) will be on this line. Graphing these points will create a vertical line.
If the standard form eliminates the x-term, such as -2y = 4, then any value can be chosen for x but the y-value will remain -2. Resulting in a set of ordered pairs of the form (x, -2). Graphing these points will create a horizontal line.