4. Let I denote the set of irrational numbers. (a). Prove that if r e I then V n E Z*, nr € I.

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A full step by step solution please to the attached image hwk question. Both part a and b and c.

4. Let I denote the set of irrational numbers.
(a). Prove that if r E I then Vn e Z*, nr E I.
(b). Explain True or False of statement: “If S is an infinite subset of I, then S is uncountable."
(c). Prove by contradiction: "I is uncountable."
Transcribed Image Text:4. Let I denote the set of irrational numbers. (a). Prove that if r E I then Vn e Z*, nr E I. (b). Explain True or False of statement: “If S is an infinite subset of I, then S is uncountable." (c). Prove by contradiction: "I is uncountable."
Expert Solution
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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