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Inquiry about the properties of square roots

  1. Sep 16, 2009 #1
    What is the proof that states that if the square root of a natural number is not another natural number, it must be irrational? In other words, the square root of a natural number must be either natural or irrational.
  2. jcsd
  3. Sep 16, 2009 #2
    Use unique factorization into primes.
  4. Sep 16, 2009 #3


    Staff: Mentor

    And continuing with g_edgar's advice, a perfect square will always have pairs of equal factors. E.g., 81 = 9*9, 100 = 10*10 and so on.
  5. Sep 16, 2009 #4
    The critical component is that the square root of a prime number is irrational and by extension so is the square root of any square-free number. The proofs of these facts are not necessarily straight forward.

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