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Homework Help: Finding a logical formula (wff) for an englsh expression

  1. Sep 22, 2012 #1
    1. The problem statement, all variables and given/known data

    Suppose P(x) is a statement with a free variable x. Find a formula, using logical symbols, that means "there are exactly two values of x for which P(x) is true."


    2. Relevant equations



    3. The attempt at a solution


    (∃x)(∃y)(∀z)(P(x) ∧ P(y) ∧ P(z) → ( x=z ∨ y=z) ∧ x≠y)

    Is this valid?
     
  2. jcsd
  3. Sep 22, 2012 #2

    Simon Bridge

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