The graph the the function $y = f(x)$ is shown below. To evaluate the function, drag the cross-hair (green) on the horizontal axis to the desired input value. Then measure the height of the graph from the vertical axis (red) to find the output value.

1. Evaluate $f(-4)$
   $f(-4) =$
2. Evaluate $f(-1)$
   $f(-1) =$
3. Evaluate $f(0)$
   $f(0) =$
4. Evaluate $f(2)$
   $f(2) =$

Notice how each input yields only one result (there is only one answer for each input) but some inputs have the same output value. It’s no coincidence: the graph passes the vertical line test!