Results 1 to 2 of 2

Math Help - Find x.

  1. #1
    Junior Member
    Joined
    Feb 2011
    Posts
    56

    Find x.

    Given x^(1/2)-5x^(1/4)+6=0 , find x. I tried but couldn't get the correct answer. The answers given are 16 and 81. Please kindly show the working as well. Thanks.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,548
    Thanks
    1418
    \displaystyle x^{1/2} - 5x^{1/4} + 6 = 0

    \displaystyle (x^{1/4})^2 - 5x^{1/4} + 6 = 0.

    Let \displaystyle X = x^{1/4} and the equation becomes

    \displaystyle X^2 - 5X + 6 = 0

    \displaystyle (X - 2)(X - 3) = 0

    \displaystyle X - 2 = 0 or \displaystyle X - 3 = 0

    \displaystyle X = 2 or \displaystyle X = 3

    \displaystyle x^{1/4} = 2 or \displaystyle x^{1/4} = 3

    \displaystyle x = 2^4 or \displaystyle x = 3^4

    \displaystyle x = 16 or \displaystyle x = 81.
    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