Results 1 to 3 of 3

Math Help - Find K so that....

  1. #1
    Newbie
    Joined
    Sep 2011
    Posts
    23

    Find K so that....

    X^3 -12X^2 + K

    find K for
    Two Different Zeros
    Three Different Zeros ( I believe K=X for this one )
    Only one Real Zero

    Any help would be greatly appreciated thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Dec 2007
    From
    Ottawa, Canada
    Posts
    3,102
    Thanks
    68

    Re: Find K so that....

    Quote Originally Posted by waleedrabbani View Post
    X^3 -12X^2 + K
    Is that suppose to be X^3 - 12X^2 + K = 0 ?
    You're not showing an equation!!

    Anyhow, if K=0 then:
    x^3 - 12x^2 = 0
    x^2(x - 12) = 0
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor Reckoner's Avatar
    Joined
    May 2008
    From
    Baltimore, MD (USA)
    Posts
    1,024
    Thanks
    75
    Awards
    1

    Re: Find K so that....

    Quote Originally Posted by waleedrabbani View Post
    X^3 -12X^2 + K

    find K for
    Two Different Zeros
    Three Different Zeros ( I believe K=X for this one )
    Only one Real Zero
    The discriminant of the cubic equation ax^3 + bx^2 + cx + d = 0 is given by

    d = 18abcd - 4b^3d + b^2c^2 - 4ac^3 - 27a^2d^2.

    So the cubic equation X^3 - 12X^2 + K has a discriminant of

    d = 6912K - 27K^2.

    Now determine which values of K make the discriminant positive, negative, or zero.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 8
    Last Post: March 22nd 2011, 04:57 PM
  2. Replies: 2
    Last Post: July 5th 2010, 08:48 PM
  3. Replies: 1
    Last Post: February 17th 2010, 03:58 PM
  4. Replies: 0
    Last Post: June 16th 2009, 12:43 PM
  5. Replies: 2
    Last Post: April 6th 2009, 08:57 PM

/mathhelpforum @mathhelpforum