Results 1 to 2 of 2

Math Help - Descartes Rule of Signs

  1. #1
    Junior Member
    Joined
    Apr 2008
    Posts
    27

    Descartes Rule of Signs

    Use Descartes's Rule of Signs to determine the possible number of negative real zeros for the given function.

    g(x)=-3x^7+x^5-x^2+4

    So far I have this:

    g(-x)=-3(-x)^7+1(-x)^5-1(x)^2+4
    g(-x)=-3x^7-x^5-x^2+4

    1 negative real root.
    Last edited by theevilp0ptart; May 6th 2008 at 07:20 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Aug 2007
    From
    USA
    Posts
    3,111
    Thanks
    2
    g(x) has -+-+ That's 3, so 3 or 1 positive.

    g(-x) has +--+ That's 2, so 2 or 0 negative.

    ALL the negative powers change sign for g(-x). You missed the x^{7} term.
    Last edited by TKHunny; November 22nd 2009 at 12:51 PM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 5
    Last Post: June 6th 2011, 02:18 AM
  2. Using Descartes' Rule of Signs
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: May 21st 2010, 01:47 PM
  3. Descartes rule of signs
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: March 19th 2009, 06:50 AM
  4. [SOLVED] Descartes's Rule Of Signs
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: October 4th 2008, 03:56 PM
  5. Descartes' Rule of Signs Help
    Posted in the Algebra Forum
    Replies: 1
    Last Post: January 17th 2008, 10:45 AM

Search Tags


/mathhelpforum @mathhelpforum