The statement is false because a graph can represent relationships that are not functions. A function is defined as a relation that assigns exactly one output (y value) for each input (x value). In contrast, some graphs can have multiple y values for a single x value.
For example, consider the circle given by the equation x² + y² = r². When you input the x value of, say, 1, there are two corresponding y values (1 and -1). This violates the definition of a function because the same x value maps to two different y values.
In summary, not every graph represents a function. A valid function requires that each x must relate to only one y.