In mathematics, the term "domain" is often used to refer to the set of input values for a function. When we say that the domain of a function is all real numbers, we mean that the function can accept any real number as its input.
For example, the function f(x) = 2x can accept any real number as its input, since we can multiply any real number by 2. Therefore, the domain of f(x) is all real numbers.
On the other hand, some functions may have restrictions on their input values. For instance, the function g(x) = 1/x has a restricted domain, since we cannot divide by zero. Therefore, the domain of g(x) is all real numbers except for zero.
It's worth noting that not all functions have a domain that includes all real numbers. Some functions, such as trigonometric functions like tangent, have a domain that is limited to a specific range of real numbers.
In summary, when we say that the domain of a function is all real numbers, we mean that the function can accept any real number as its input.
