Results 1 to 6 of 6

Math Help - word problem using polynomials

  1. #1
    Junior Member
    Joined
    May 2009
    Posts
    36

    word problem using polynomials

    hi i need help with this question, i got some of it...

    The volume of a cardboard box is x^3 - 8x^2 + 17x - 10 Factor this polynomial.

    i got (x-1)(x-5)(x-2)

    if these factors represent the length, width, and height, find the demensions of a box that has a volume of 20cm^3

    i got ...
    x^3 - 8x^2 + 17x - 10 = 20
    x^3 - 8x^2 + 17x - 30 = 0

    i then found a factor of (x-6), and after putting that through senthetic division i was left with  x^2 - 2x + 5 , but this dosent really factor, so i think i've done something wrong...help please
    Last edited by extraordinarymachine; December 16th 2009 at 11:43 AM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,807
    Thanks
    116
    Quote Originally Posted by extraordinarymachine View Post
    hi i need help with this question, i got some of it...

    The volume of a cardboard box is x^3 - 8x^2 + 17x + 10 Factor this polynomial.

    i got (x-1)(x-5)(x-2)<<< = x^3-8x^2+17x-10

    if these factors represent the length, width, and height, find the demensions of a box that has a volume of 20cm^3

    i got ...
    x^3 - 8x^2 + 17x + 10 = 20
    x^3 - 8x^2 + 17x\bold{\color{red} - 10} = 0

    i then found a factor of (x-6), and after putting that through senthetic division i was left with  x^2 - 2x + 5 , but this dosent really factor, so i think i've done something wrong...help please
    ...
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    May 2009
    Posts
    36
    Quote Originally Posted by earboth View Post
    .The volume of a cardboard box is Factor this polynomial.

    i got (x-1)(x-5)(x-2)<<< = x^3-8x^2+17x-10

    if these factors represent the length, width, and height, find the demensions of a box that has a volume of

    i got ...

    ..
    i'm not sure what you did here, or what your trying to say.
    the question was actually  x^3 - 8x^2 + 17x - 10
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,807
    Thanks
    116
    Quote Originally Posted by extraordinarymachine View Post
    i'm not sure what you did here, or what your trying to say.
    the question was actually  x^3 - 8x^2 + 17x - 10
    I noticed that you have corrected the typo in your first post.

    Now all your calculations are OK.

    You can't factor x^2-2x+5 because this term is greater zero for all x \in \mathbb{R}.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    May 2009
    Posts
    36
    and here i thought i was wrong lol
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,807
    Thanks
    116
    Quote Originally Posted by extraordinarymachine View Post
    and here i thought i was wrong lol
    To finish the original question:

    You certainly have noticed that you get only one solution: x = 6.

    Thus the demensions of the box are 5 * 1 * 4 which yields indeed 20.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Doing some more polynomials and word problems
    Posted in the Algebra Forum
    Replies: 2
    Last Post: September 15th 2011, 03:11 AM
  2. Replies: 7
    Last Post: April 7th 2011, 12:38 PM
  3. One small problem with cyclotomic polynomials
    Posted in the Advanced Algebra Forum
    Replies: 3
    Last Post: April 27th 2010, 07:27 PM
  4. Problem Involving Polynomials and Their Roots
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: October 30th 2009, 08:14 AM
  5. HELP!polynomials:word problem equations
    Posted in the Algebra Forum
    Replies: 2
    Last Post: March 19th 2009, 04:59 AM

Search Tags


/mathhelpforum @mathhelpforum