Results 1 to 5 of 5

Math Help - Algebraic equation with fractions

  1. #1
    Newbie
    Joined
    Sep 2010
    Posts
    4

    Question Algebraic equation with fractions

    Hi, I need help with this equation!

    \frac {9} {x-10} - \frac {210}{x^2 -100} = 1

    I have tried to cross multiply and factor the question and end up with

     x(-9x^2-9x+1200) = 0

    If that is in the ballpark can you help me factor that or am I completely wrong?

    The book asks for

    Solutions are x1= and x2= . Important Note: x1 denotes the smaller solution.
    Last edited by tofuwrice; September 11th 2010 at 08:52 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    10,964
    Thanks
    1008
    Sorry but this is unreadable. Please use brackets where they're needed or learn some basic LaTeX. There is an entire subforum here dedicated to learning to use LaTeX.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Sep 2010
    Posts
    4
    Huzzah, I have fixed my original post. Sorry for the inconvenience.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    10,964
    Thanks
    1008
    Quote Originally Posted by tofuwrice View Post
    Hi, I need help with this equation!

    \frac {9} {x-10} - \frac {210}{x^2 -100} = 1

    I have tried to cross multiply and factor the question and end up with

     x(-9x^2-9x+1200) = 0

    If that is in the ballpark can you help me factor that or am I completely wrong?

    The book asks for

    Solutions are x1= and x2= . Important Note: x1 denotes the smaller solution.
    Cross multiplying is a method that is "in the ballpark", but the easier way is to get a common denominator.

    Note that x^2 - 100 = (x - 10)(x + 10).


    So \frac{9}{x - 10} - \frac{210}{x^2 - 100} = 1

    \frac{9(x + 10)}{(x - 10)(x + 10)} - \frac{210}{(x - 10)(x + 10)} = 1

    \frac{9(x + 10) - 210}{(x - 10)(x + 10)} = 1

    \frac{9x + 90 - 210}{x^2 - 100} = 1

    \frac{9x - 120}{x^2 - 100} = 1

    9x - 120 = 1(x^2 - 100)

    9x - 120 = x^2 - 100

    0 = x^2 - 9x + 20

    0 = (x - 4)(x - 5)

    x - 4 = 0 or x - 5 = 0

    x = 4 or x = 5.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Sep 2010
    Posts
    4
    omg, i am literally smacking my head. I can't believe i didn't see this simple solution. Thanks a lot!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Algebraic Fractions
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 17th 2011, 01:27 AM
  2. Algebraic Fractions
    Posted in the Algebra Forum
    Replies: 2
    Last Post: December 2nd 2010, 05:10 PM
  3. Algebraic Fractions
    Posted in the Algebra Forum
    Replies: 3
    Last Post: October 14th 2010, 09:14 AM
  4. Algebraic fractions FML
    Posted in the Algebra Forum
    Replies: 5
    Last Post: September 9th 2010, 08:05 PM
  5. Replies: 0
    Last Post: April 28th 2010, 09:53 AM

Search Tags


/mathhelpforum @mathhelpforum