Analyse the following statements concerning real numbers and provide detailed proofs…

MATHEMATICS · Multi-part · A Level · Mathematics · Proof · Proof

Problem

Analyse the following statements concerning real numbers and provide detailed proofs or counter-examples as required. (i) S:  ∀x∈R ∃y∈R (y2=x)S:\; \forall x\in\mathbb R\,\exists y\in\mathbb R\,(y^{2}=x). Decide whether SS is true or false and justify your answer. (ii) If SS is false, exhibit one explicit real number that serves as a counter-example and explain why it invalidates the statement. (iii) Modify the domain of xx so that the sentence ∀x ∃y (y2=x)\forall x\,\exists y\,(y^{2}=x) becomes true. State the revised domain and prove the truth of the resulting statement. (iv) Consider the reordered quantification T:  ∃y∈R ∀x∈R (y2=x)T:\; \exists y\in\mathbb R\,\forall x\in\mathbb R\,(y^{2}=x). Determine the truth value of TT and justify your conclusion.

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