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Homework Help: Cuse these difference quotients

  1. Aug 29, 2008 #1
    Cuse these difference quotients!!!

    1. The problem statement, all variables and given/known data
    http://www.webassign.net/www14/symImages/5/8/30f1e141e81c6a3333af41547f8ff2.gif

    Evaluate the difference quotient for the given function

    http://www.webassign.net/www14/symImages/4/6/bda668fa415dbf5d0c9c2ba4c031d2.gif


    2. Relevant equations
    n/a


    3. The attempt at a solution
    I seem to have the wrong mindset while doing these.

    I got 0.

    Actually, I dont really know exactly what I'm even going for here.
     
    Last edited by a moderator: Apr 23, 2017
  2. jcsd
  3. Aug 29, 2008 #2

    Dick

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    Re: Cuse these difference quotients!!!

    It's not zero. It's a function of x. Why don't you show us what you did? Just substitute the given f(x) into the difference quotient.
     
  4. Aug 29, 2008 #3
    Re: Cuse these difference quotients!!!

    My main thing is that I dont know what the outcome should look like.

    It was during the last few weeks of my senior year of high school so I didnt exactly make it to class every day and I missed this stuff. Its coming back to bite me in college now.
     
  5. Aug 29, 2008 #4

    Dick

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    Re: Cuse these difference quotients!!!

    I told you, just substitute the form for f(x) into the difference quotient and try and do some algebra to simplify it. What is f(5)? This isn't a big conceptual problem.
     
  6. Aug 29, 2008 #5
    Re: Cuse these difference quotients!!!

    Later on you will see that the slope of the tangent line at a point say P(a,f(a)), is given by:

    [tex]\lim_{x\rightarrow a}\frac{f(x)-f(a)}{x-a}=f'(a)[/tex]

    And only the quotient [tex] \frac{f(x)-f(a)}{x-a}[/tex] is the slope of secat line.

    So, you are given a function f(x) and then asked to find the quotient.

    [tex]\frac{f(x)-f(5)}{x-5}[/tex] so what u want to do is replace f(x) with what you are given, in other words, write the function f(x)=... whatever it equals, and then for f(5), you first want to evalulate f(5)=...whatever it equals. You evaluate f(5) by plugging 5 in

    [tex]f(x)=\frac{x+7}{x+5}[/tex]
     
    Last edited by a moderator: Apr 23, 2017
  7. Aug 29, 2008 #6

    HallsofIvy

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    Re: Cuse these difference quotients!!!

    Dick said "Why don't you show us what you did? " Why will you not do that?
     
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