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Linear Approximation

  1. May 17, 2009 #1
    1. The problem statement, all variables and given/known data

    Here is a picture of the problem: http://i3.photobucket.com/albums/y62/Phio/34.jpg" [Broken]

    2. Relevant equations

    y - f(c) = f '(c) (x - c)

    3. The attempt at a solution

    1/(5+x)^1/2 = (5 + x) ^ -1/2 = (1/5)^(1/2) * (1 + x/5)^(-1/2)

    I have this. But I don't know if i'm on the right track...
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. May 17, 2009 #2


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    I don't know what you are doing! You have rewritten the formula in a couple of different ways but you seem to have made no attempt to find either f'(c) or f(c), which you need to use "y- f(c)= f'(c)(x- c)".
  4. May 17, 2009 #3


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    Hi Fiorella! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    (I've no idea why you think "y - f(c) = f '(c) (x - c)" is relevant :confused: … but anyway:)

    The answers given are clearly wrong :frown:

    at x = 0, f(x) = 1/√5, which does not match.

    But your method is correct …

    just carry on regardless! :smile:
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