Results 1 to 3 of 3

Thread: Equation

  1. #1
    Member jacs's Avatar
    Joined
    Jan 2006
    From
    Sydney
    Posts
    119
    Thanks
    8

    Equation

    hi, i can't sort out what to do with this one:

    $\displaystyle
    \sqrt{2m-3}=\sqrt{m+7} - 2
    $


    thanks

    jacs
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member OReilly's Avatar
    Joined
    Mar 2006
    Posts
    340
    $\displaystyle \begin{array}{l}
    \sqrt {2m - 3} = \sqrt {m + 7} - 2 \\
    \left( {\sqrt {2m - 3} } \right)^2 = \left( {\sqrt {m + 7} - 2} \right)^2 \\
    2m - 3 = m + 7 - 4\sqrt {m + 7} + 4 \\
    2m - 3 - m - 7 - 4 = - 4\sqrt {m + 7} \\
    \end{array}
    $
    $\displaystyle \begin{array}{l}
    m - 14 = - 4\sqrt {m + 7} \\
    \left( {m - 14} \right)^2 = \left( {4\sqrt {m + 7} } \right)^2 \\
    m^2 - 28m + 196 = 16(m + 7) \\
    m^2 - 28m + 196 - 16m - 112 = 0 \\
    m^2 - 44m + 84 = 0 \\
    \end{array}
    $
    $\displaystyle m_{1/2} = \frac{{44 \pm \sqrt {1936 - 336} }}{2} = \frac{{44 \pm \sqrt {1600} }}{2} = \frac{{44 \pm 40}}{2}$
    $\displaystyle m_1 = 42 \wedge m_2 = 2$

    Solution is $\displaystyle m=2$.
    Last edited by OReilly; Apr 9th 2006 at 05:43 AM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member jacs's Avatar
    Joined
    Jan 2006
    From
    Sydney
    Posts
    119
    Thanks
    8
    thanks OReilly, i see it now. I got half way and then didnt know how to proceed, but it is just manipulating them cleverly.

    thanks,for that

    i appreciate it

    jacs
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: Apr 11th 2011, 01:17 AM
  2. Partial differential equation-wave equation - dimensional analysis
    Posted in the Differential Equations Forum
    Replies: 3
    Last Post: Aug 28th 2009, 11:39 AM
  3. Replies: 2
    Last Post: May 18th 2009, 12:51 PM
  4. Replies: 2
    Last Post: Apr 28th 2009, 06:42 AM
  5. Replies: 1
    Last Post: Oct 23rd 2008, 03:39 AM

Search Tags


/mathhelpforum @mathhelpforum