Ordering on Positive Integers is Equivalent to Ordering on Natural Numbers
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Theorem
Let $u, v \in \Z_{>0}$ be natural numbers.
Consider the mapping $\phi: \N_{>0} \to \Z_{>0}$ defined as:
- $\forall u \in \N_{>0}: \map \phi u = u'$
where $u' \in \Z$ denotes the (strictly) positive integer $\eqclass {b + u, b} {}$.
Let $u', v' \in \Z_{>0}$ be strictly positive integers.
Then:
- $u > v \iff u' > v'$
Proof
Let $u' = \eqclass {b + u, b} {}$.
Let $v' = \eqclass {c + v, c} {}$.
Then:
\(\ds u'\) | \(>\) | \(\ds v'\) | ||||||||||||
\(\ds \leadstoandfrom \ \ \) | \(\ds \eqclass {b + u, b} {}\) | \(>\) | \(\ds \eqclass {c + v, c} {}\) | |||||||||||
\(\ds \leadstoandfrom \ \ \) | \(\ds b + u + c\) | \(>\) | \(\ds c + v + b\) | |||||||||||
\(\ds \leadstoandfrom \ \ \) | \(\ds u\) | \(>\) | \(\ds v\) |
$\blacksquare$
Sources
- 1951: Nathan Jacobson: Lectures in Abstract Algebra: Volume $\text { I }$: Basic Concepts ... (previous) ... (next): Introduction $\S 5$: The system of integers