see the explanations of domain and range in the following threads:

http://www.mathhelpforum.com/math-he...lus-notes.html (post #2)

http://www.mathhelpforum.com/math-he...ain-range.html

http://www.mathhelpforum.com/math-he...ions-help.html

http://www.mathhelpforum.com/math-he...-function.html

http://www.mathhelpforum.com/math-he...ain-range.html

you should know how to find the domain and range for several classes of functions: polynomials, logs, radical, rationals, trigonometric functions. i think the threads i gave cover them all. if not, ask about them