One of the most common functions that has a domain of all real numbers is the linear function, represented as f(x) = mx + b, where m and b are constants. This function is defined for every real number x you may choose.
Another example would be the quadratic function f(x) = x², which is also defined for all real numbers. Even more, the exponential function f(x) = e^x and the sine and cosine functions are valid for all real numbers.
What this means in practical terms is that you can input any real number into these functions and expect a valid output. In contrast, a function like f(x) = 1/x does not have a domain of all real numbers because it is undefined when x = 0.
In summary, if you’re looking for functions that can accept any real number as input, consider linear, quadratic, exponential, and trigonometric functions as prime examples.