Results 1 to 6 of 6

Math Help - synthetic division

  1. #1
    Newbie
    Joined
    Oct 2009
    Posts
    22

    synthetic division

    I am not sure what is actually going on here, helping daughtet.

    P(x)=4fortth - 7xthird + 66x - 72

    Upside down division sign below.

    4/ 1 -7 0 66 -72
    -----------------
    4 -12 -48 72
    ---------------
    1 -3 -12 -48 72
    -----------------

    1 -3 -12 18 (o)=>4 is a zero of p(x)

    xthird -3xsecond -12x + 18

    1-3-12 18 I can't find a number that works here. I am not sure what I am supposed to be trying to do.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,700
    Thanks
    454
    Quote Originally Posted by jonb View Post
    I am not sure what is actually going on here, helping daughtet.

    P(x)=4fortth - 7xthird + 66x - 72

    Upside down division sign below.

    4/ 1 -7 0 66 -72
    -----------------
    4 -12 -48 72
    ---------------
    1 -3 -12 -48 72
    -----------------

    1 -3 -12 18 (o)=>4 is a zero of p(x)

    xthird -3xsecond -12x + 18

    1-3-12 18 I can't find a number that works here. I am not sure what I am supposed to be trying to do.

    is this your polynomial?

    if P(x) = x^4 - 7x^3 + 66x - 72
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Oct 2009
    Posts
    22
    yes
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,700
    Thanks
    454
    Quote Originally Posted by jonb View Post
    I am not sure what is actually going on here, helping daughtet.

    P(x)=4fortth - 7xthird + 66x - 72

    Upside down division sign below.

    4/ 1 -7 0 66 -72
    -----------------
    4 -12 -48 72
    ---------------
    1 -3 -12 -48 72
    -----------------

    1 -3 -12 18 (o)=>4 is a zero of p(x)

    xthird -3xsecond -12x + 18

    1-3-12 18 I can't find a number that works here.

    try synthetic division with x = -3
    ...
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Oct 2009
    Posts
    22
    ok...that worked. I am trying to figure out why this works.

    thanks
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,700
    Thanks
    454
    Quote Originally Posted by jonb View Post
    ok...that worked. I am trying to figure out why this works.

    thanks
    why it works is the Rational Root Theorem.

    Mathwords: Rational Root Theorem
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Synthetic Division
    Posted in the Algebra Forum
    Replies: 2
    Last Post: July 5th 2010, 05:32 PM
  2. Synthetic division
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: November 13th 2009, 08:09 AM
  3. Synthetic Division
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: September 2nd 2009, 02:57 PM
  4. Polynomial division vs synthetic division
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 9th 2009, 05:49 AM
  5. Synthetic Division
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: January 20th 2007, 05:37 AM

Search Tags


/mathhelpforum @mathhelpforum