The expression "f(3) = 3^2 = 9" represents a mathematical function, where f is the function and 3 is the input value. The notation "3^2" means "3 squared," which is the same as multiplying 3 by itself. Therefore, when you calculate 3 squared, you get 9. In this case, the function f takes the input 3 and produces the output 9. This demonstrates a basic principle of functions in mathematics, where each input corresponds to a specific output based on the function's rule. Here, the rule is to square the input value.