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Linear Algebra, Theory And Applications, 2012a

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22 PRELIMINARIES<br />

Definition 1.8.5 The Archimedean property states that whenever x ∈ R, anda>0, there<br />

exists n ∈ N such that na > x.<br />

Proposition 1.8.6 R has the Archimedean property.<br />

Proof: Suppose it is not true. Then there exists x ∈ R and a>0 such that na ≤ x<br />

for all n ∈ N. Let S = {na : n ∈ N} . By assumption, this is bounded above by x. By<br />

completeness, it has a least upper bound y. By Proposition 1.7.3 there exists n ∈ N such<br />

that<br />

y − a

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