MacLaurin Series and Ratio Test for f(x) = loge(1-x)

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SUMMARY

The discussion centers on finding the MacLaurin series for the function f(x) = loge(1-x) and determining its interval of convergence. Participants emphasize the need to compute derivatives at zero, specifically f(0), f'(0), and f''(0), to construct the series. The Ratio Test is highlighted as a method to establish the interval of convergence, requiring an open interval (e, f) based on strict inequalities. The conversation aims to clarify the steps necessary for evaluating the series and convergence criteria.

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  • Understanding of MacLaurin series expansion
  • Knowledge of derivatives and their evaluation at specific points
  • Familiarity with the Ratio Test for series convergence
  • Basic concepts of logarithmic functions and their properties
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  • Calculate the first few derivatives of f(x) = loge(1-x) at x = 0
  • Learn how to apply the Ratio Test to determine series convergence
  • Research methods for finding intervals of convergence for power series
  • Explore examples of MacLaurin series for other functions for comparative understanding
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pandamon
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For f(x) = loge(1-x)
Clarification: The question isn’t loge(1+x), it’s loge(1-x)

a) Find the MacLaurin series: f(0) +f'(0)x + f''(0)/2! + f'''(0)/3!...etc

My question is, to what extent do I keep applying the series to, since the series goes on forever and there are no constraints specified.

b) Also, I’m having trouble finding the interval of convergence for the MacLauren series, how do I find the interval of convergence?

c) According to the question I am given, I was to find an open interval (e,f) from b) since the statement of the ratio test uses a strict inequality.
And now I have to use an appropriate test of series convergence for the MacLaurin series found at the start at x = e and x = f

I am clueless as to how to attempt these questions, could somebody please show me the steps? I am keen to understand how to go about tackling these questions.

Thank you very much, I really appreciate your help.
 
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You could start by trying to find f(0), f'(0), f''(0) etc. Any ideas on that? Can you find a general way to write the nth derivative of f evaluated at 0?
 
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