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Combining f(x) and g(x)?

  1. Dec 1, 2009 #1
    1. The problem statement, all variables and given/known data

    Apologies for any trouble, but I'm not going to post any numbers, as my school is very sensitive about plagiarism and the like in homework. I only need some help in figuring out what to do.

    I'm given a table of x values 1 to 5, and for each, corresponding y-values for two functions: f(x) and g(x). So my table has three rows x, f(x), and g(x).

    I have to find the limit of [2f(x) - 3g(x)] as x approaches 1.

    I can do g(f(x)), but... Af(x) - Bg(x)? What...?

    I know limits are calculus stuff, but what I really need help with here is manipulating g(x) and f(x), and that should be precalculus... right?

    2. Relevant equations
    None that I know of

    3. The attempt at a solution
    I'm stumped. The first thing that did cross my mind was substituting the y values I'm given from the table into f(x) and g(x), but... that can't be right! I get a number that makes no sense.
  2. jcsd
  3. Dec 1, 2009 #2
    I fail to see the problem. [2f(x) - 3g(x)] doesnt involve compound functions.
  4. Dec 1, 2009 #3
    Hmm, so should I just post this in the calculus forum? I just don't know how to find the limit of [2f(x) - 3g(x)] as x approaches 1.
  5. Dec 2, 2009 #4


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    [tex]\lim_{x\to a} (Af(x)+ Bg(x))= A(\lim_{x\to a} f(x))+ B(\lim_{x\to a} g(x))[/tex]

    I would think you would have learned that well before
    [tex]\lim_{x\to a} f(g(x))[/tex]
  6. Dec 2, 2009 #5
    Ah, thank you so much!
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