Results 1 to 8 of 8

Math Help - help please - powers/log question

  1. #1
    Newbie
    Joined
    Oct 2012
    From
    israel
    Posts
    4

    help please - powers/log question

    Hi all,
    This question appeared in a logarithm chapter.

    (√(4+√15))^x + (√(4-√15))^x = 8

    i simply can't crack it...
    thanks,

    Raz.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,617
    Thanks
    1581
    Awards
    1

    Re: help please - powers/log question

    Quote Originally Posted by razidan View Post
    Hi all,
    This question appeared in a logarithm chapter.
    (√(4+√15))^x + (√(4-√15))^x = 8
    By inspection x=2.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Oct 2012
    From
    israel
    Posts
    4

    Re: help please - powers/log question

    Can I see the full solution please?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,617
    Thanks
    1581
    Awards
    1

    Re: help please - powers/log question

    Quote Originally Posted by razidan View Post
    Can I see the full solution please?
    So far as I know, there is no simple solution other than by inspection.
    I also think that is the whole point of this question.
    I have seen hundreds like it.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Oct 2012
    From
    israel
    Posts
    4

    Re: help please - powers/log question

    Really? I would guess they want me to somehow translate it into a logarithmic equation, that's the whole purpose of that chapter...
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,617
    Thanks
    1581
    Awards
    1

    Re: help please - powers/log question

    Quote Originally Posted by razidan View Post
    Really? I would guess they want me to somehow translate it into a logarithmic equation, that's the whole purpose of that chapter...
    Well did you post it correctly?
    Is it product and not a sum?
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Oct 2012
    From
    israel
    Posts
    4

    Re: help please - powers/log question

    help please - powers/log question-powers.jpg

    number 4.30
    Follow Math Help Forum on Facebook and Google+

  8. #8
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,617
    Thanks
    1581
    Awards
    1

    Re: help please - powers/log question

    Quote Originally Posted by razidan View Post
    Click image for larger version. 

Name:	powers.JPG 
Views:	3 
Size:	25.5 KB 
ID:	25000
    number 4.30
    I see you posted correctly.
    Then it is just a poorly constructed problem if you are expect to use any method other than inspection.

    It is no different from solving 16^x+9^x=25. There is no elementary algebraic solution.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Arithmetic : Powers and Roots Question
    Posted in the Algebra Forum
    Replies: 6
    Last Post: January 6th 2011, 05:11 AM
  2. equating powers - quick question
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 18th 2010, 01:35 AM
  3. Another question about large powers of matrices
    Posted in the Advanced Algebra Forum
    Replies: 6
    Last Post: August 19th 2009, 05:43 PM
  4. question abt powers
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: August 8th 2009, 05:52 AM
  5. AS question on powers, sim eq, and inequalities
    Posted in the Advanced Algebra Forum
    Replies: 3
    Last Post: December 8th 2007, 08:08 AM

Search Tags


/mathhelpforum @mathhelpforum