Final answer:
To find f(-3) for the function y = 9 + 3x, substitute -3 for x to get f(-3) = 9 + 3(-3) = 9 - 9 = 0. Thus, f(-3) is 0.
Step-by-step explanation:
Understanding the equation y = 9 + 3x, we know that to find f(-3) we simply need to substitute x with -3 in the equation. So, f(-3) would be calculated as:
f(-3) = 9 + 3(-3) = 9 - 9 = 0.
Therefore, the function value f(-3) is 0. This process demonstrates how to evaluate a linear function at a given x-value by plugging the value into the function's equation and simplifying.