If you were to graph 2 lines the three things that could happen are...

1. The two lines could intersect.
    If two lines cross each other, or intersect, the point where they intersect is the solution.

2. The two lines could be parallel.
    If two lines never cross, they are parallel so they don't share any point; therefore there is no solution.

3. The two lines could coincide.
    If two lines are on top of each other, or coincide, they share all points and have infinite solutions.

Before we begin our examples, you need to recall how to write equations in slope-intercept form (y = mx + b).  If you need to review return to the notes from section 8-4.  Once you remember slope-intercept form, click here to go on to some examples.