Results 1 to 4 of 4

Math Help - proof prob

  1. #1
    Member GAdams's Avatar
    Joined
    Apr 2007
    Posts
    171
    Awards
    1

    proof prob

    y = x^2 + x + 11 The value of y is a prime number when x = 0, 1, 2 and 3

    The following statement is not true:
    y = x^2 + x + 11 is always a prime number when x is an integer’

    Show that the statement is not true.

    Thanks,
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Reckoner's Avatar
    Joined
    May 2008
    From
    Baltimore, MD (USA)
    Posts
    1,024
    Thanks
    75
    Awards
    1

    Smile

    Quote Originally Posted by GAdams View Post
    The following statement is not true:
    y = x^2 + x + 11 is always a prime number when x is an integer’

    Show that the statement is not true.
    Just give a counterexample: x=10 will work.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member GAdams's Avatar
    Joined
    Apr 2007
    Posts
    171
    Awards
    1
    Quote Originally Posted by Reckoner View Post
    Just give a counterexample: x=10 will work.
    I was (mistakenly) reading it as a proof problem. But yes, that works. Thanks.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor Reckoner's Avatar
    Joined
    May 2008
    From
    Baltimore, MD (USA)
    Posts
    1,024
    Thanks
    75
    Awards
    1

    Smile

    Quote Originally Posted by GAdams View Post
    I was (mistakenly) reading it as a proof problem. But yes, that works. Thanks.
    Well, really, it is a proof. But since we are only trying to prove the existence of a single value (specifically, you are trying to prove that there is at least one value for which the expression is not prime) the proof consists merely of finding such a value.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: April 12th 2011, 11:13 AM
  2. [SOLVED] Independent Prob Proof
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: February 3rd 2011, 06:09 PM
  3. Log Prob.
    Posted in the Algebra Forum
    Replies: 3
    Last Post: February 3rd 2009, 05:14 PM
  4. Int. prob
    Posted in the Calculus Forum
    Replies: 4
    Last Post: September 19th 2008, 06:12 PM
  5. Prob Qn'
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: April 11th 2008, 12:51 AM

Search Tags


/mathhelpforum @mathhelpforum