1. The problem is to understand when a graph represents a relation that is also a function. 2. The key rule is the Vertical Line Test: A graph represents a function if and only if every vertical line intersects the graph exactly once. 3. This means if you draw any vertical line (a line parallel to the y-axis) anywhere on the graph, it should cross the graph at only one point. 4. If a vertical line crosses the graph more than once, the graph does not represent a function because a function can only assign one output (y-value) for each input (x-value). 5. In summary, the vertical line test helps us visually check if a relation is a function by ensuring no vertical line intersects the graph more than once.