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March 19th, 2017, 06:43 PM  #1 
Member Joined: Feb 2017 From: henderson Posts: 36 Thanks: 0  Find the tangent line approximation
Find the tangent line approximation for f(x) = 1/x near x=8 so I used the f(a) +f'(a)(xa) f = 1/x f' = 1/x^2 I end up writing y  1/8 = 1/64 (x + 8) my answer I get is 1/64  1/4, but it's wrong so I am stuck. :/ Any help? Last edited by skipjack; March 19th, 2017 at 11:12 PM. 
March 19th, 2017, 07:15 PM  #2 
Senior Member Joined: Sep 2015 From: USA Posts: 1,780 Thanks: 919 
$f(x)=\dfrac 1 x$ $f'(x) = \dfrac{1}{x^2}$ $f(8) = \dfrac 1 8$ $f'(8) = \dfrac{1}{64}$ $f(x) \approx \dfrac 1 8  \dfrac {1}{64}\left(x  8\right) = \dfrac{1}{64}x +\dfrac 1 4$ you're trying to produce a function of $x$, not a number. 

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approximation, find, line, tangent 
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