The graph of $f(x) = x^2 - 3x - 4$ is shown at right. Use the graph to solve:

1. $f(x) = 0$  

   Hint (a):

   Think of $f(x)$ as $y$.

2. $f(x) ≥ 0$ 

   Answer (b):

   $x ≤ -1$ or $x ≥ 4$

3. $f(x) ≤ 0$