Advanced Engineering Mathematics
Advanced Engineering Mathematics
10th Edition
ISBN: 9780470458365
Author: Erwin Kreyszig
Publisher: Wiley, John & Sons, Incorporated
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A full step by step solution please to the attached image hwk question. Both part a and b and c.

## Problem 4

Let \( I \) denote the set of **irrational numbers**.

### Part (a)
**Prove** that if \( r \in I \) then \( \forall n \in \mathbb{Z}^+, nr \in I \).

### Part (b)
**Explain** True or False for the statement: "If \( S \) is an **infinite subset** of \( I \), then \( S \) is **uncountable**."

### Part (c)
**Prove by contradiction**: " \( I \) is **uncountable**."
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Transcribed Image Text:## Problem 4 Let \( I \) denote the set of **irrational numbers**. ### Part (a) **Prove** that if \( r \in I \) then \( \forall n \in \mathbb{Z}^+, nr \in I \). ### Part (b) **Explain** True or False for the statement: "If \( S \) is an **infinite subset** of \( I \), then \( S \) is **uncountable**." ### Part (c) **Prove by contradiction**: " \( I \) is **uncountable**."
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Step 1

PART A

Let rI and nZ+

Suppose nrI i.e. nrI i.e. nrQ i.e. nz is rational so, 

nr=ab where a,bZ

Therefore,  r=anb

Clearly, a,bZ so nbZ and nb0

So r is rational which contradict the fact that r is irrational.

Hence nr is irrational.

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