Results 1 to 8 of 8
Like Tree5Thanks
  • 1 Post By jewelmaule
  • 1 Post By princeps
  • 1 Post By princeps
  • 1 Post By ibdutt
  • 1 Post By Prove It

Math Help - factorisation of a quadratic equation that is a fraction :/

  1. #1
    Newbie
    Joined
    Mar 2013
    From
    Australia
    Posts
    4
    Thanks
    1

    factorisation of a quadratic equation that is a fraction :/

    Hey guys im stuck on an equation and just cant seem to get the right answer. I know there must be something wrong with my working. Could someone please show me how you multiply out the denominator to solve this equation.

    1+ 6/x-1 = 1/x+1

    Thank you in advance for any help.
    Thanks from jpritch422
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Nov 2011
    From
    Crna Gora
    Posts
    420
    Thanks
    64

    Re: factorisation of a quadratic equation that is a fraction :/

    Hi , multiply equation by (x-1)(x+1)
    Thanks from jewelmaule
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Mar 2013
    From
    Australia
    Posts
    4
    Thanks
    1

    Re: factorisation of a quadratic equation that is a fraction :/

    Quote Originally Posted by princeps View Post
    Hi , multiply equation by (x-1)(x+1)
    Thank you for your quick reply. I tried that and still cant seem to get the correct answer. I know the answer because I have checked and I cant even work backwards to get it. Ill show my working out and maybe someone will know where im going wrong..

    1+ 6/x-1 = 1/x+1
    1+6(x+1) = (x-1)
    1+6x+6-x-1 = 0
    5x+6 = 0
    )
    (
    )
    But the proper answer is= X2+5x+6=0
    x=-3 & -2

    I cant seem to find where x2 came from.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Senior Member
    Joined
    Nov 2011
    From
    Crna Gora
    Posts
    420
    Thanks
    64

    Re: factorisation of a quadratic equation that is a fraction :/

    You have to multiply 1 by (x-1)(x+1) also .
    Last edited by princeps; March 21st 2013 at 10:12 PM.
    Thanks from jewelmaule
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Super Member
    Joined
    Jul 2012
    From
    INDIA
    Posts
    822
    Thanks
    209

    Re: factorisation of a quadratic equation that is a fraction :/

    In such cases go by the following algorithm.
    Step-1: Multiply the equation be the LCM of the denominator which in this case is (x-1)(x=1)
    .(x-1)(x+1)[ 1 + 6/(x-1) = 1/(x+1) OR x^2 -1 + 6(x+1) = (x-1)
    Step 2: Simplify the equation
    x^2 -1 + 6x+6 = x-1
    x^2 -1 + 6x+6 -x+1= 0
    x^2 + 5x+6 = 0
    (x+3)(x+2) = 0
    etc.
    Thanks from jewelmaule
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Mar 2013
    From
    Australia
    Posts
    4
    Thanks
    1

    Re: factorisation of a quadratic equation that is a fraction :/

    Ahhh I think I get it now! Thanks heaps for all the help.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    10,969
    Thanks
    1009

    Re: factorisation of a quadratic equation that is a fraction :/

    Quote Originally Posted by jewelmaule View Post
    Hey guys im stuck on an equation and just cant seem to get the right answer. I know there must be something wrong with my working. Could someone please show me how you multiply out the denominator to solve this equation.

    1+ 6/x-1 = 1/x+1

    Thank you in advance for any help.
    I assume that your equation is \displaystyle 1 + \frac{6}{x-1} = \frac{1}{x + 1}. Some brackets where they're needed would be nice... Anyway...

    \displaystyle \begin{align*} 1 + \frac{6}{x - 1} &= \frac{1}{x + 1} \\ \frac{x-1}{x-1} + \frac{6}{x-1} &= \frac{1}{x+1} \\ \frac{x+5}{x-1} &= \frac{1}{x+1} \\ \frac{(x+5)(x+1)}{(x-1)(x+1)} &= \frac{x-1}{(x-1)(x+1)} \\ (x+5)(x+1) &= x-1 \\ x^2 + 6x + 5 &= x-1 \\ x^2 +5x + 6 &= 0 \\ (x + 3)(x+2) &= 0 \\ x+ 3 = 0\textrm{ or } x+2 &= 0 \\ x = -3 \textrm{ or } x &= -2 \end{align*}
    Thanks from jewelmaule
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Newbie
    Joined
    Mar 2013
    From
    Australia
    Posts
    4
    Thanks
    1

    Re: factorisation of a quadratic equation that is a fraction :/

    Quote Originally Posted by Prove It View Post
    I assume that your equation is \displaystyle 1 + \frac{6}{x-1} = \frac{1}{x + 1}. Some brackets where they're needed would be nice... Anyway...
    Thank you for your help. Yeah I have been trying to figure out how everyone gets their equations in that format on this forum.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 6
    Last Post: March 31st 2010, 05:09 AM
  2. Factorisation quadratic
    Posted in the Algebra Forum
    Replies: 2
    Last Post: February 28th 2010, 02:02 PM
  3. Replies: 7
    Last Post: June 24th 2009, 02:54 AM
  4. Turning a fraction into a quadratic
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: December 2nd 2008, 10:03 AM
  5. expansion and factorisation diophantine equation
    Posted in the Number Theory Forum
    Replies: 1
    Last Post: February 17th 2007, 04:53 PM

Search Tags


/mathhelpforum @mathhelpforum