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# What does domain mean in math?

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Domain, in math, is defined as the set of all possible values that can be used as input values in a function. A simple mathematical function has a domain of all real numbers because there isn't a number that can be put into the function and not work.

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An example in which the domain is not all real numbers is when a function results in an undefined number. For the function y= 3/(x-1), all real numbers work except for 1. When 1 is entered into the function, the end result is 3 divided by 0, which is an undefined number.

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## Related Questions

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A relation is a set of numbers that have a relationship through the use of a domain and a range, while a function is a relation that has a specific set of numbers that causes there to be only be one range of numbers for each domain of numbers. All functions are relations, but all relations are not functions.

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The identity function in math is one in which the output of the function is equal to its input, often written as f(x) = x for all x. The input-output pair made up of x and y are always identical, thus the name identity function. This holds true not only for the set of all real numbers, but also for the set of all real functions. Often considered mathematically trivial, the identity function is the basis for all other functions.

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In mathematics, a function is a relation between a set of inputs and a set of permissible outputs. Specifically, each input into a function has exactly one corresponding and correct output.