What can be determined at the y-intercept?

The y-intercept of a graph represents the point where the line crosses the y-axis. This occurs when the value of x is zero. Therefore, at the y-intercept, one can determine the starting value of the function, which is the output (or y-value) when x equals zero. This starting value provides crucial information about the behavior of the function at the beginning of its domain.

In contrast, the other options do not accurately describe the significance of the y-intercept. The direction change of a line usually pertains to points where it turns, rather than where it intersects the y-axis. The maximum value of a graph can occur at various points depending on the function, not specifically at the y-intercept. Lastly, an endpoint of a line is not defined by the y-intercept, especially in the context of straight lines which extend infinitely in both directions unless stated otherwise. Thus, the starting value of the function at the y-intercept becomes the correct choice.