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Two Restrictions That Define Special Function Types
publish date: 2026/05/23 18:47:51.803842 UTC
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The general definition of a function places two conditions only on elements of the domain. If we impose analogous restrictions on elements of the codomain, which two special function types result?
Correct Answer
One-one (injective) function and onto (surjective) function
Explanation
General functions only restrict domain elements: (i) every domain element has an image, (ii) each domain element has exactly one image. Restricting the codomain analogously gives: (i) every codomain element is an image → onto/surjective; (ii) each codomain element has at most one pre-image → one-one/injective.
Reference
Introduction to Differential Calculus (Systematic Studies with Engineering Applications for Beginners) - 2012
