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Ch. 11 - Power Series
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 11, Problema 11.R.51

Limits by power series Use Taylor series to evaluate the following limits.


lim ₙ → ₄ ln (x - 3)/(x² - 16)

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First, recognize that the limit is as \(x\) approaches 4 for the expression \(\frac{\ln(x - 3)}{x^2 - 16}\). Notice that directly substituting \(x = 4\) gives \(\frac{\ln(1)}{16 - 16} = \frac{0}{0}\), an indeterminate form, so we need to use a series expansion to evaluate the limit.
Next, rewrite the denominator \(x^2 - 16\) as \((x - 4)(x + 4)\) to better understand its behavior near \(x = 4\).
Now, expand the numerator \(\ln(x - 3)\) as a Taylor series around \(x = 4\). Let \(h = x - 4\), so \(x - 3 = 1 + h\). The Taylor series for \(\ln(1 + h)\) around \(h = 0\) is \(\ln(1 + h) = h - \frac{h^2}{2} + \frac{h^3}{3} - \cdots\).
Similarly, express the denominator in terms of \(h\): \(x^2 - 16 = (4 + h)^2 - 16 = 8h + h^2\). This gives the denominator as \(8h + h^2\) near \(h = 0\).
Finally, write the original limit expression in terms of \(h\) using the expansions: \(\frac{h - \frac{h^2}{2} + \cdots}{8h + h^2}\). Simplify this expression by factoring out \(h\) from numerator and denominator, then analyze the limit as \(h \to 0\) to find the value of the limit.

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