1. Not a function – 0 maps to both −3 and 3. 2. Not a function – 2 maps to both −2 and 2, and 5 maps to both −5 and 5. 3. Not a function – 4 maps to both −2 and 2, and 9 maps to both −3 and 3. 4. Function 5. Function 6. Function 7. Not a function – Since (1,−2 2 ) and (1,2 2 ) are both on the graph, it does not pass vertical line test. 8. Not a function – Since (1,−1) and (1,1) are both on the graph, it does not pass the vertical line test. 9. Not a function – Since (1,−1) and (1,1) are both on the graph, it does not pass the vertical line test. 10. Function 11. Function 12. Function 13. Not a function – Since (0,5) and (0,−5) are both on the graph, it does not pass the vertical line test. 14. Not a function – Since (0,4) and (0,−4) are both on the graph, it does not pass the vertical line test. 15. Function 16. Function 17. Not a function – Since (0,−1) and (0,−3) are both on the graph, it does not pass the vertical line test. 18. Function 19. a) 5 b) 1 c) −3 20. a) 1 b) −5 c) 0