Chapter 1 - Linear Functions and Change - 1.1 Functions and Function Notation - Exercises and Problems for Section 1.1 - Exercises and Problems - Page 7: 13

f(x)=0 x= 0, 4, or 8

We know f(x)= y, so when f(x)=0, y=0. Thus, it is a matter of finding x coordinates of points where y=0. We get x= 0, 4, or 8 because those are all of the x coordinates along the graph of f where y=0.