Results 1 to 13 of 13

Math Help - rational exp - simplify

  1. #1
    Junior Member
    Joined
    Mar 2011
    Posts
    34

    rational exp - simplify

     \frac{2}{6x^2} + \frac{4}{9x^3}

    I need a common denominator?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    Try \displaystyle 6x^2 \times 9x^3

    Or find the lowest common mulitple of the 2. Maybe \displaystyle 18x^3
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Mar 2011
    Posts
    34
     \frac{18}{54x^5}+\frac{24}{54x^5} = \frac{42}{54x^5}

    How's this look?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    That's a good start but its not quite correct.

     \displaystyle \frac{2}{6x^2}+\frac{4}{9x^3}


     \displaystyle \frac{2}{6x^2}\times \frac{9x^3}{9x^3}+\frac{4}{9x^3}\times \frac{6x^2}{6x^2}


     \displaystyle \frac{\dots}{54x^5}+\frac{\dots}{54x^5}
    Last edited by pickslides; March 20th 2011 at 04:24 PM. Reason: Bad Latex
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Mar 2011
    Posts
    34
     \frac{18x^3}{54x^5}+\frac{24x^2}{54x^5} = \frac{42x^5}{54x^5} = \frac{42}{54}
    Follow Math Help Forum on Facebook and Google+

  6. #6
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    You're not done cancelling yet. Recall your six times table

    You're on the right track though
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member
    Joined
    Mar 2011
    Posts
    34
    Oh.  \frac{7}{9}
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    Quote Originally Posted by reallylongnickname View Post
     \frac{18x^3}{54x^5}+\frac{24x^2}{54x^5} = \frac{42x^5}{54x^5} = \frac{42}{54}
    Be careful with your like terms  \displaystyle 18x^3+24x^2 \neq 42x^5
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Junior Member
    Joined
    Mar 2011
    Posts
    34
    Is this the final answer?

     = \frac{18x^3 + 24x^2}{54x^5}
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    Quote Originally Posted by reallylongnickname View Post
    Is this the final answer?

     = \frac{18x^3 + 24x^2}{54x^5}
    That is better, I would conclude that  \displaystyle \frac{18x^3 + 24x^2}{54x^5}= \frac{6\times 3x^3 + 6\times 4x^2}{6\times 9x^5} = \frac{6( 3x^3 +  4x^2)}{6\times 9x^5}=  \frac{ 3x^3 +4x^2}{ 9x^5}
    Follow Math Help Forum on Facebook and Google+

  11. #11
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,490
    Thanks
    1391
    Quote Originally Posted by pickslides View Post
    That is better, I would conclude that  \displaystyle \frac{18x^3 + 24x^2}{54x^5}= \frac{6\times 3x^3 + 6\times 4x^2}{6\times 9x^5} = \frac{6( 3x^3 +  4x^2)}{6\times 9x^5}=  \frac{ 3x^3 +4x^2}{ 9x^5}
    \displaystyle = \frac{x^2(3x + 4)}{9x^5} = \frac{3x + 4}{9x^3}...
    Follow Math Help Forum on Facebook and Google+

  12. #12
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,536
    Thanks
    1391
    In fact, it would have been better to use 18x^3 as your common denominator rather than 18x^5.
    Follow Math Help Forum on Facebook and Google+

  13. #13
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,490
    Thanks
    1391
    Or even better still, note that \displaystyle \frac{2}{6x^2} = \frac{1}{3x^2}, then your LCD is \displaystyle 9x^3...
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Simplify rational expression
    Posted in the Algebra Forum
    Replies: 1
    Last Post: December 6th 2011, 07:46 AM
  2. simplify rational expression
    Posted in the Algebra Forum
    Replies: 3
    Last Post: March 21st 2010, 07:50 PM
  3. simplify a rational fraction
    Posted in the Algebra Forum
    Replies: 4
    Last Post: September 3rd 2009, 08:31 AM
  4. Simplify Rational Expression
    Posted in the Algebra Forum
    Replies: 4
    Last Post: January 19th 2009, 04:19 PM
  5. simplify this rational function (logs)?
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 16th 2008, 11:52 PM

Search Tags


/mathhelpforum @mathhelpforum