How do we know that the domain and range are real numbers from a functional graph?

like if the question gives you a graph and ask you to find the domain and range, sometimes, the answer is real numbers.





How do we know when?? help plzzzzzzHow do we know that the domain and range are real numbers from a functional graph?
[Answer: Either of these two sites should help you out:





http://www.purplemath.com/modules/fcns2.鈥?/a>


http://www.analyzemath.com/DomainRange/D鈥?/a> ]