Final answer:
The domain of any quadratic function is (-∞, ∞), as they are defined for all real values of 'x' and extend infinitely in both directions on the x-axis.
Step-by-step explanation:
The domain of any quadratic function is (-∞, ∞), which in interval notation is written as (-∞, ∞). This is because quadratic functions, which are mathematical functions known as second-order polynomials, are defined for all real values of 'x'. A quadratic function typically has the form f(x) = ax² + bx + c, where a, b, and c are constants and a ≠ 0. For any real value of 'x', you can substitute it into the function and get a corresponding real number 'y'. Hence, quadratic functions do not have any restrictions on their domains and they extend infinitely in both the positive and negative directions of the x-axis.