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!

Small part of a larger problem

  1. Sep 12, 2009 #1
    1. The problem statement, all variables and given/known data
    I am trying to figure out of [tex]\frac{9}{x+h}[/tex] can be split into some thing like
    [tex]\frac{9}{x} + ?[/tex]


    2. Relevant equations
    None


    3. The attempt at a solution
    I am not sure what to do. I am trying to do this as part of a larger limits problem.
     
    Last edited: Sep 12, 2009
  2. jcsd
  3. Sep 12, 2009 #2
    I don't believe you can change one to the other. The difference between 9/(x + h) and 9/x is that the first is shifted -h units to the left of the graph of 9/x. 9/x + something would shift the graph of 9/x up something units.
     
  4. Sep 12, 2009 #3
    You would need to add it to a fraction whose denominator 'a' had the property xa = x + h, or a = (x + h)/x. Unfortunately, there is no fraction that you can add that will not affect the numerator as well.
     
  5. Sep 13, 2009 #4
    Damn, ok thanks for your help, both of you.
     
  6. Sep 14, 2009 #5

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    What you can do is get a common denominator and subtract fractions.
    [tex]\frac{9}{x+h}- \frac{9}{x}= \frac{9x}{x(x+h)}- \frac{9(x+h)}{x(x+h)}[/tex]
    [tex]= \frac{9x- 9(x+h)}{x(x+h)}= \frac{-9h}{x(x+h)}[/tex]
    and you should be able to complete the derivative.
     
    Last edited: Sep 14, 2009
  7. Sep 14, 2009 #6
    :surprisedAhhhhh, I see said the blind man to the deaf dog with no ears. Thank you!!!!!

    Btw how did you figure out that thats what I was trying to do? That was pretty amazing. :D
     
    Last edited: Sep 14, 2009
  8. Sep 14, 2009 #7

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Hey, after some time here you get used to figuring out what people are really asking!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Small part of a larger problem
  1. Conics Problem Part 5 (Replies: 2)

Loading...