The graph represents the piecewise function:

In the range -1 ≤ x < 1, the graph is shown as constant at y=4.

In the range 3 ≤ x ≤ 5, the graph is shown with a slope of 1. If that line were extended, it would cross the y-axis at y=-1, so has equation y=x-1.

The graph shown here has a solid dot at (x, f(x)) = (1, 4), so does not correspond to the function written below it, which is not defined at x=1.

The two blanks in the function definition can be filled in with

4

x-1