Analyzing f(x): Determine the Linear Function's Increasing or Decreasing Behavior

To solve this problem, we'll analyze the graph of the function:

• Step 1: Carefully observe the given graph of $f(x)$.
• Step 2: Evaluate the overall trend of the graph.
• Step 3: Determine if the function is increasing, decreasing, or constant based on the slope.

Now, let's go through the solution:
Step 1: Observing the graph, we see that the curve starts at a higher coordinate on the y-axis and moves downwards as it progresses from left to right.
Step 2: This indicates a negative slope, as the y-values decrease while the x-values increase.
Step 3: Reasoning from the previous observations, it is clear that as $x$ increases, the function's value $f(x)$ decreases.

Therefore, the correct conclusion is that the function $f(x)$ is decreasing.