Use the graph to predict the number of CDs the students at your high school bought in 2008

What are the domain and range of f(x)=[1/5]x

Which approach to the theory-and-research cycle does the following sequence reflect: (1) specific observations suggest generalizations, (2) generalizations produce a tentative theory, (3) the theory is tested through the formation of hypotheses, and (4) hypotheses may provide suggestions for additional observations?

What is the frequency of the sinusoidal graph?