Results 1 to 2 of 2

Math Help - arithmetic

  1. #1
    Junior Member
    Joined
    Apr 2009
    Posts
    29

    arithmetic

    hello,

    Prove that \forall n \in \mathbb{N} , there's no number k\in \mathbb{N} and 3n^2 + 3n +7= k^3
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by linda2005 View Post
    hello,

    Prove that \forall n \in \mathbb{N} , there's no number k\in \mathbb{N} and 3n^2 + 3n +7= k^3
    i haven't worked out the details, but a proof by contradiction should work. assume there is such a k. what would the solution to 3n^2 + 3n + 7 - k^3 = 0 look like? would n be a natural number or even an integer at all? try the quadratic formula, see what happens
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. A sum on arithmetic mean...
    Posted in the Algebra Forum
    Replies: 1
    Last Post: January 30th 2010, 03:47 AM
  2. Arithmetic Progression or Arithmetic Series Problem
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: October 8th 2009, 01:36 AM
  3. arithmétic
    Posted in the Algebra Forum
    Replies: 0
    Last Post: February 16th 2008, 09:22 AM
  4. Arithmetic Mean
    Posted in the Algebra Forum
    Replies: 2
    Last Post: January 10th 2007, 04:50 PM
  5. Arithmetic Mean
    Posted in the Algebra Forum
    Replies: 1
    Last Post: November 8th 2006, 08:01 AM

Search Tags


/mathhelpforum @mathhelpforum