Results 1 to 5 of 5

Math Help - Fining the Zeros of this polynomial.

  1. #1
    Junior Member
    Joined
    Mar 2007
    Posts
    45

    Fining the Zeros of this polynomial.

    Hello. I am having a hard time finding the Zeros to this polynomial function. Could you please explain the steps. I keep coming up with really odd answers when I factor that couldn't possibly be the zeros to this function. Thanks.

    P(X)=-x^3+21x-20
    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 Mathfailure View Post
    Hello. I am having a hard time finding the Zeros to this polynomial function. Could you please explain the steps. I keep coming up with really odd answers when I factor that couldn't possibly be the zeros to this function. Thanks.

    P(X)=-x^3+21x-20
    Here
    Attached Thumbnails Attached Thumbnails Fining the Zeros of this polynomial.-poly.gif  
    Follow Math Help Forum on Facebook and Google+

  3. #3
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Here is the graph, if you're interested
    Attached Thumbnails Attached Thumbnails Fining the Zeros of this polynomial.-p-x-.jpg   Fining the Zeros of this polynomial.-closeup.jpg  
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Mar 2007
    Posts
    45
    Do you have to divide? We haven't learned how to divide anything into a polynomial yet. Thanks for the quick reply
    Follow Math Help Forum on Facebook and Google+

  5. #5
    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 Mathfailure View Post
    Do you have to divide? We haven't learned how to divide anything into a polynomial yet. Thanks for the quick reply
    No you don't, but dividing makes life simplier. you can actually find the other roots the same way we found the first one. that is, we plug in the factors of the lone constant into the equation to see if we get zero.

    the factors of 20 are: +/- 1, +/- 2,+/- 4,+/- 5,+/- 10, +/- 20

    so i started by plugging in +1, and as luck would have it, that was a root, that is, P(1)=0. i then used that to divide. however, i could have continued by plugging in the other numbers to see which gives zero. eventually you would have found that +4 and -5 are roots
    Last edited by Jhevon; April 1st 2007 at 11:57 PM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Zeros of a polynomial
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: May 8th 2010, 08:12 PM
  2. Polynomial Degrees and Zeros
    Posted in the Algebra Forum
    Replies: 1
    Last Post: December 1st 2008, 04:39 AM
  3. polynomial function with 3 zeros
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 13th 2008, 12:33 AM
  4. Zeros of polynomial
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: October 30th 2007, 11:09 AM
  5. Polynomial Zeros
    Posted in the Algebra Forum
    Replies: 4
    Last Post: December 6th 2005, 09:08 AM

Search Tags


/mathhelpforum @mathhelpforum