11. YES. Because each x-value is only used once (no duplicate x-coordinates)
12. range is the y-values. the lowest it goes is -2 (with an open dot), then it goes to +2 (with an open dot). then there is a separate line where y = 4.
Answer: (-2, 2) U [4, 4]
13. f(-1): when x = -1, y = ??? (do not count the open dot!)
Answer: 1
14. f(3): when x = 3, y = ??? (do not count the open dot!)
Answer: 4
