1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Rationalizing a numerator

  1. Sep 11, 2011 #1
    1.
    Haven't done this type of math in a long time, here's the question:
    1. Rationalize the numerator
    a) (√x - 3) / (x - 9)


    Can't get the answer for the life of me. The textbook says (1)/(√x - 3)

    the / dictates division.




    2. Relevant equations
    Question: (√x - 3) / (x - 9)
    Answer: (1)/(√x - 3)




    3. The attempt at a solution

    I multiplied the top and bottom by the conjugate of the numerator (√x + 3)
    and ended up getting (x-9)/(x√x + 3x - 9√x - 27)

    and I get stumped here.
     
  2. jcsd
  3. Sep 11, 2011 #2

    LCKurtz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Instead of multiplying the denominator out like that, leave it factored and see if you can cancel factors.
     
  4. Sep 11, 2011 #3

    symbolipoint

    User Avatar
    Homework Helper
    Education Advisor
    Gold Member

    From here, which looks good, (x-9)/(x√x + 3x - 9√x - 27)
    = [itex]\frac{x-9}{\sqrt{x}(x-9)+3(x-9}[/itex]
    = [itex]\frac{x-9}{(x-9)(\sqrt{x}-3)}[/itex]
    ... can then be simplified.
     
  5. Sep 11, 2011 #4
    Alright, I got it guys!
    Thanks :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Rationalizing a numerator
  1. Rational Expressions (Replies: 3)

  2. Rational Inequalities (Replies: 2)

  3. Rational inequality (Replies: 7)

Loading...