Surjection/Examples/Non-Surjection/2x+1 Function on Integers
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Example of Mapping which is Not a Surjection
Let $f: \Z \to \Z$ be the mapping defined on the set of integers as:
- $\forall x \in \Z: \map f x = 2 x + 1$
Then $f$ is not a surjection.
Proof
Consider $y = 2 n$ for some $n \in \Z$.
There exists no $x \in \Z$ such that $\map f x = y$.
Thus by definition $f$ is not a surjection.
$\blacksquare$
Sources
- 1965: J.A. Green: Sets and Groups ... (previous) ... (next): Chapter $3$. Mappings: Exercise $2 \ \text {(iv) (b)}$