(b) Define x = a³ as the real number satisfying the equality (x · x)· x = a. For a > 0, you may assume as true that as > 0. Use only this definition and the axiomatic definition of the real numbers, to prove that a < b% whenever 0 < a < b. You may assume that for every a E R, there is a number as in R. Justify each step and use only one axiom per step.

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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I was wondering how to solve b,c,d, and e.  (All of them) 

(b) Define x = a3 as the real number satisfying the equality (x · x) · x = a. For a > 0, you may
assume as true that as > 0. Use only this definition and the axiomatic definition of the real
numbers, to prove that
aš < b3
whenever 0 <a<b. You may assume that for every a E R, there is a number aš in R. Justify
each step and use only one axiom per step.
(c) Let us assume the facts from part (b) for all a, b e R, i.e. aš < b3 whenever a < b. Let
SCR be bounded above and non-empty. Define
Š = {x € R]x* € S}.
Prove that sup
= sup
using the definition of the least upper bound.
(d) Consider the sequence {an} C Q given by
п 3 2, 4, 7, 17
n+1
2n
otherwise
Prove the sequence is Cauchy from the definition of a Cauchy sequence.
(e) In the context of the Cauchy sequence construction of the real numbers, find the inverses
-{an} and {an}-1 for the sequence of part (d). No partial credit. Only give the final answer
for this part.
Transcribed Image Text:(b) Define x = a3 as the real number satisfying the equality (x · x) · x = a. For a > 0, you may assume as true that as > 0. Use only this definition and the axiomatic definition of the real numbers, to prove that aš < b3 whenever 0 <a<b. You may assume that for every a E R, there is a number aš in R. Justify each step and use only one axiom per step. (c) Let us assume the facts from part (b) for all a, b e R, i.e. aš < b3 whenever a < b. Let SCR be bounded above and non-empty. Define Š = {x € R]x* € S}. Prove that sup = sup using the definition of the least upper bound. (d) Consider the sequence {an} C Q given by п 3 2, 4, 7, 17 n+1 2n otherwise Prove the sequence is Cauchy from the definition of a Cauchy sequence. (e) In the context of the Cauchy sequence construction of the real numbers, find the inverses -{an} and {an}-1 for the sequence of part (d). No partial credit. Only give the final answer for this part.
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