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Q.a) Write the negation of each of the following statements: p: For every real number x, x²>x; q: For every real number x, either x>1 or x<1. b) "Mathematics is fun" - check whether this sentence is a statement.

West Bengal WbchseWest Bengal HS First Year (WBCHSE Class XI) Annual Examination 2018Subjective· 4mImportance★★★★★est
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Negating a universal ('for every') gives an existential ('there exists') with the inner condition negated; a sentence is a statement only if it is objectively true or false, which a subjective claim like 'fun' is not.

a) Negation of pp: 'For every real number xx, x2>xx^2>x.' Negating ∀x,x2>x\forall x, x^2>x gives ∃x\exists x such that x2≤xx^2\le x. So: 'There exists a real number xx such that x2≤xx^2\le x.'

Negation of qq: 'For every real number xx, either x>1x>1 or x<1x<1.' Negating ∀x,(x>1∨x<1)\forall x,(x>1\lor x<1) gives ∃x\exists x such that eg(x>1)∧eg(x<1) eg(x>1)\land eg(x<1), i.e. x≤1x\le1 and x≥1x\ge1, i.e. x=1x=1. So: 'There exists a real number xx such that x=1x=1 (i.e., neither x>1x>1 nor x<1x<1).'

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