Chap 1 The Number System

The set s x q x2 2 is bounded above we can take k

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Unformatted text preview: if there exists a number K ∈ R such that x ≤ K for every x ∈ S . The number K is called an upper bound of the set S . COMPLETENESS AXIOM. Suppose that S is a non-empty set of real numbers and S is bounded above. Then there is a real number M ∈ R such that M ≤ K for every upper bound K of the set S , and that M > L for any real number L that is not an upper bound of S . Remark. The crucial assertion is that this number M is a real number. The set S = {x ∈ Q : x2 < 2} √ is bounded above. We can take K = 2 or K = 52000 . However, we clearly have M = 2. 1.4. Further Discussion on the Real Numbers In this optional section, we shall first of all demonstrate the equivalence of the condition (WO) and the two forms of the Principle of induction. Proof of the equivalence of the Well-ordering principle and the two Principles of induction. Our first step is to show that the condition (WO) is equivalent to the Principle of induction (strong form) (PIS). ((WO) ⇒ (PIS)) Suppose th...
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This note was uploaded on 02/01/2009 for the course MATH 2343124 taught by Professor Staff during the Fall '08 term at UCSD.

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