Short Answer 
A function defines a relationship between input (x) and output (y), represented as f(x). To find f(3) on a graph, locate x = 3 on the x-axis, trace vertically to the curve, and identify the corresponding output value on the y-axis. For instance, if the graph intersects at y = 4, then f(3) = 4.
Step 1: Understanding Functions
A function is a specific relationship that connects an input value, denoted as x, to an output value, represented as y. This means that for every input, there is a unique output. Functions are often expressed as f(x), indicating the function evaluated at x.
Step 2: Finding f(3) on a Graph
To find the value of f(3) on a graph, you need to locate where the input value x = 3 aligns with the function. This involves identifying the point on the x-axis where x = 3 and tracing vertically to intersect the graph. The corresponding point on the y-axis gives you the output value.
Step 3: Identifying the Output Value
Once you have traced from the point where x = 3 to the curve of the graph, the point at which you hit the curve will provide the output value f(3). For example, if the intersection yields y = 4, then it can be stated that f(3) = 4. This demonstrates how to extract values from a function visually.