Results 1 to 5 of 5

Math Help - quadratic problem

  1. #1
    Newbie Miasmagasma's Avatar
    Joined
    Nov 2009
    Posts
    21

    quadratic problem

    i tried to times everything by 4x to take away the surd but i got nowhere.

    solve the following equation

    x-8 = 2√x
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    Quote Originally Posted by Miasmagasma View Post
    i tried to times everything by 4x to take away the surd but i got nowhere.

    solve the following equation

    x-8 = 2√x
    x-8 = 2\sqrt{x}

    square both sides ...

    x^2 - 16x + 64 = 4x

    x^2 - 20x + 64 = 0

    (x - 4)(x-16) = 0

    now ... which solution works in the original equation?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    10,969
    Thanks
    1010
    Quote Originally Posted by Miasmagasma View Post
    i tried to times everything by 4x to take away the surd but i got nowhere.

    solve the following equation

    x-8 = 2√x
    x - 8 = 2\sqrt{x}

    (x - 8)^2 = (2\sqrt{x})^2

    x^2 - 16x + 64 = 4x

    x^2 - 20x + 64 = 0

    (x - 16)(x - 4) = 0

    x = 4 or x = 16.


    Darn, beaten...
    Last edited by mr fantastic; December 9th 2009 at 04:52 PM. Reason: m --> r
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie Miasmagasma's Avatar
    Joined
    Nov 2009
    Posts
    21
    thanks guys, i made the stupid error of squaring the 8 initially, rather than the whole side.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    ... please note that only one of the two solutions is valid.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] quadratic equation, A.P. and G.P. related problem problem
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: August 20th 2011, 08:43 AM
  2. Quadratic problem...!
    Posted in the Algebra Forum
    Replies: 10
    Last Post: July 19th 2011, 02:18 PM
  3. quadratic problem
    Posted in the Algebra Forum
    Replies: 2
    Last Post: February 26th 2009, 01:55 AM
  4. quadratic problem
    Posted in the Algebra Forum
    Replies: 2
    Last Post: September 26th 2008, 05:19 PM
  5. quadratic problem
    Posted in the Algebra Forum
    Replies: 2
    Last Post: August 23rd 2007, 03:39 AM

Search Tags


/mathhelpforum @mathhelpforum