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!

Solving a limit help

  1. Sep 29, 2012 #1
    I have the limit:
    [tex]
    \lim_{x\rightarrow +2} {\frac{f(x)-5}{x-2}}=5
    [/tex]
    And i want to find the:
    [tex]
    \lim_{n\rightarrow +2} {f(x)}
    [/tex]
    Can i say that [itex]f(x)-5=5*(x-2)[/itex]
    And then find the limit?
    Thank you
     
    Last edited: Sep 29, 2012
  2. jcsd
  3. Sep 29, 2012 #2
    There is some confusion between n and x. Fix that. Then observe that as x (or n) goes to 2, the denominator goes to zero.
     
  4. Sep 29, 2012 #3
    And why is that a problem?
    Both parts will be equal to 0.
     
  5. Sep 29, 2012 #4
    Because that would prevent you from using the formula you wanted.

    But think about it. You have a finite limit of a ratio, whose denominator goes to zero. What can be said about the limit of its numerator in this case?
     
  6. Sep 29, 2012 #5

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Yes, the denominator goes to 0. So what must the numerator go to in order that a limit exist?
     
  7. Sep 29, 2012 #6

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    No, because there are, in fact, an infinite number of possible functions, f. f(x)= 5(x- 2)+5 is just one of them.

    Yes, the denominator goes to 0. So what must the numerator go to in order that a limit exist?
     
  8. Sep 30, 2012 #7
    The numerator should be zero.
    So we have: [itex]f(2)-5=0[/itex] Am i right?

    Something about before,
    Why you said that there are infinite number of functions f that can satisfy that limit?
    One is [itex]f(x)=5(x-1)[/itex], can you give me another example?
    Thank you
     
    Last edited: Sep 30, 2012
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Solving a limit help
  1. Help solving limits! (Replies: 9)

Loading...