The domain of the function f(x) = 3x² is the set of all real numbers. This is because there are no restrictions on the values that x can take in this function. You can substitute any real number into the equation, and it will produce a valid output.
To break it down, the function is a quadratic function and is defined for all x values. Unlike functions that involve square roots or denominators that can be zero, this particular function does not impose any limitations on x. Therefore, when you’re asked about the domain, you can confidently state that it is all real numbers, which can be represented in interval notation as (-∞, ∞).