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Function (mathematics) - Wikipedia, the free encyclopedia |
 | | Thus, the "is a square root of" relation is a function, and it contains for example, the pairs (3, 9) and (-3, 9); while the converse, "is the square of" relation, is not a function because it contains both the pairs (9, 3) and (9, −3), and 3 is not equal to −3. |
 | | In this definition, a function is a special case of a relation, in particular a function is a relation in which every first element has a unique second element. |
 | | The number of computable functions from integers to integers is countable, because the number of possible algorithms is. The number of all functions from integers to integers is higher: the same as the cardinality of the real numbers. |
| en.wikipedia.org /wiki/Mathematical_function (3457 words) |
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