What is the value of f(3) if f(x) = x^2 + 2x?

To determine the value of f(3) using the function f(x) = x^2 + 2x, you start by substituting 3 for x in the function.

First, compute the square of 3:

3^2 = 9.

Next, calculate 2 times 3:

2 * 3 = 6.

Now, add these two results together:

9 + 6 = 15.

Thus, f(3) equals 15. This shows that when you input 3 into the function f(x), the resulting value is clearly 15, confirming that the calculation performed leads directly to that outcome.