Identify two points for each line and connect to graph lines.
Consider that x = 1 is the critical point, which gives us one included point (1, 0) marked as closed circle and one excluded point (1, 3) marked as open circle.
The second point for the first line is selected at x = - 3, which is (-3, 4) and for the second line is selected at x = 3, which is (3, 7).
See the lines attached.