Results 1 to 3 of 3

Math Help - Polynomial questions

  1. #1
    Newbie
    Joined
    Jun 2008
    Posts
    9

    Polynomial questions

    1. solve 3x^3-20x^2+33x-14<0

    2. Find the formula of this graph

    http://imageshack.us/m/841/9836/graphz.jpg
    Last edited by Ackbeet; May 11th 2011 at 01:53 AM. Reason: Splitting thread.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member Sambit's Avatar
    Joined
    Oct 2010
    Posts
    355
    1. (3x-2)(x^2-6x+7)<0
    (3x-2)[x-(3-\sqrt{2})][x-(3+\sqrt{2})]<0
    (x-\frac{2}{3})[x-(3-\sqrt{2})][x-(3+\sqrt{2})]<0
    So \frac{2}{3} , 3+\sqrt{2} , 3-\sqrt{2} are the points of interest.

    3-\sqrt{2}<x<3+\sqrt{2}, {x < 2/3}} is the solution.

    2. I am not sure whether exact formula of the graph can be derived. However, you can find an approximate formula which satisfies some values of the graph http://en.wikipedia.org/wiki/Linear_interpolation
    Last edited by Ackbeet; May 11th 2011 at 01:54 AM. Reason: Splitting thread.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,400
    Thanks
    1327
    It appears from the graph that f(-2)= 0, f(3)= 0, and f(0)= 3 and there is a minimum at x= -2 so f'(-2)= 0. If that is right and we are allowed to assume this function is cubic, then write it as f(x)= ax^3+ bx^2+ cx+ d and then f'(x)= 3ax^2+ 2bx+ c. Put f(-2)= 0, f(3)= 0, f(0)= 3 into the first equation and f'(-2)= 0 into the second to get 4 equations to solve for a, b, c, and d.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Polynomial function questions~
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: December 8th 2011, 04:04 PM
  2. Polynomial questions
    Posted in the Algebra Forum
    Replies: 4
    Last Post: January 14th 2011, 05:47 PM
  3. Three more polynomial questions
    Posted in the Algebra Forum
    Replies: 2
    Last Post: May 28th 2008, 06:21 PM
  4. two polynomial questions
    Posted in the Algebra Forum
    Replies: 2
    Last Post: May 28th 2008, 09:52 AM
  5. Another polynomial questions
    Posted in the Algebra Forum
    Replies: 1
    Last Post: February 12th 2008, 10:17 AM

Search Tags


/mathhelpforum @mathhelpforum