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Specialist Mathematics · Unit 1 · Introduction to proof · The nature of proof

Use the quantifiers ‘for all’ (∀) and ‘there exists’ (∃).

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Question 1

Use the diagram to determine which statement best describes the relationship between sets $A$ and $B$.

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Question 2

The diagram shows three mathematical statements involving quantifiers. a) Determine whether statement P is true or false. Justify your answer using algebraic reasoning. (1 mark) b) Determine whether statement Q is true or false by finding a value of \(n\) that satisfies the equation or explaining why no such value exists. (1 mark) c) Use quantifier notation to write the negation of statement R. (1 mark)

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Question 3

Use the diagram to determine which statement is true.

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Question 4

Consider the statement: "For every real number $x$, there exists a real number $y$ such that $x^2 + y = 5$." (a) Use quantifiers $\forall$ and $\exists$ to express this statement symbolically. (1 mark) (b) Determine whether this statement is true or false. Justify your answer. (1 mark) (c) Write the negation of the original statement using quantifiers $\forall$ and $\exists$, and express it in words. (1 mark)

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Question 5

Use quantifier notation to express the statement: "For every positive real number $x$, there exists a positive real number $y$ such that $y^2 = x$."

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More in The nature of proof

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Use proof by contradiction.
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Use the set notation symbol ‘is an element of’ (∈).
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