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Proof by induction

  1. Sep 29, 2014 #1
    Hi everyone,
    I am trying to learn proof by induction method from http://en.m.wikibooks.org/wiki/Algebra/Proofs/Exercises [Broken]
    And I have tried to solve the second problem attached with this post. It will be great if someone can tell me if I am wrong anywhere and then guide me.

    Thanks in advance.

    Attached Files:

    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Sep 29, 2014 #2


    Staff: Mentor

    The line quoted below is wrong.
    "It follows that (k + 1)! > 2k + 1"
    This is precisely what you need to show! You can't just wave your arms and say that "it follows that ..." without showing it.

    To show this, note that (k + 1)! = (k + 1)k!. Use your induction hypothesis (i.e., that k! > 2k) to finish the proof.

    BTW, your thread should have been posted in the Homework & Coursework section, not in the technical math sections (especially not in the Linear and Abstract Algebra section. I am moving your thread.
    Last edited by a moderator: May 7, 2017
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