Results 1 to 4 of 4

Math Help - Solving cubic equation

  1. #1
    Member
    Joined
    Oct 2008
    Posts
    88

    Solving cubic equation

    Hi, I am really out of touch with solving these.

    -t^3+10t^2-30t+32

    solving for t.
    If I can break it down to a quadratic, I should be able to do it with no problems. But I don't know how to find which factor to take out.
    Any help is great!
    Thanks in advance,
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Like a stone-audioslave ADARSH's Avatar
    Joined
    Aug 2008
    From
    India
    Posts
    726
    Thanks
    2
    Quote Originally Posted by U-God View Post
    Hi, I am really out of touch with solving these.

    -t^3+10t^2-30t+32

    solving for t.
    If I can break it down to a quadratic, I should be able to do it with no problems. But I don't know how to find which factor to take out.
    Any help is great!
    Thanks in advance,
    Roots are not real, use a calculator, the other methods will not be easy at all
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by U-God View Post
    Hi, I am really out of touch with solving these.

    -t^3+10t^2-30t+32

    solving for t.
    If I can break it down to a quadratic, I should be able to do it with no problems. But I don't know how to find which factor to take out.
    Any help is great!
    Thanks in advance,
    There is only 1 real root and its exact value is found with difficulty using Cardano's method. Why are you trying to solve this cubic, what is the whole question that it has come from?
    Last edited by mr fantastic; March 25th 2009 at 05:50 AM. Reason: Added exact value qualifier
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor chisigma's Avatar
    Joined
    Mar 2009
    From
    near Piacenza (Italy)
    Posts
    2,162
    Thanks
    5
    The only real solution can be found using the Newton-Raphson method. If tou have an equation in the form...

    f(x)=0

    ... the method consists in searching better approximation of a solution in iterative way as follows...

    x_{n+1} = x_{n} - \frac{f(x_{n})}{f ' (x_{n})}

    In our case is...

    f(x)= x^{3} -10\cdot x^{2} + 30\cdot x -32

    In few itrations you can find the only real solution x \simeq 5.75110070238\dots and after that you can reduce the equation in quadratic form...

    Kind regards

    \chi \sigma
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Solving cubic equation
    Posted in the Algebra Forum
    Replies: 13
    Last Post: April 22nd 2011, 05:16 PM
  2. Solving a cubic equation.
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: September 23rd 2010, 12:28 PM
  3. Solving a cubic equation.
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: July 6th 2010, 02:55 PM
  4. Cubic solving problem?
    Posted in the Calculators Forum
    Replies: 3
    Last Post: May 5th 2010, 03:27 PM
  5. Problem solving a cubic equation
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: March 20th 2010, 04:01 PM

Search Tags


/mathhelpforum @mathhelpforum