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Ch. 10 - Infinite Sequences and Series
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 10, Problem 10.8.25

Finding Taylor and Maclaurin Series
In Exercises 25–34, find the Taylor series generated by f at x = a.
f(x) = x³ − 2x + 4,a = 2

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Identify the function and the point about which the Taylor series is generated: here, the function is \(f(x) = x^{3} - 2x + 4\) and the center is \(a = 2\).
Recall the formula for the Taylor series of a function \(f\) about \(x = a\): \[f(x) = \sum_{n=0}^{\infty} \frac{f^{(n)}(a)}{n!} (x - a)^{n}\] where \(f^{(n)}(a)\) is the \(n\)-th derivative of \(f\) evaluated at \(x = a\).
Compute the derivatives of \(f(x)\) up to the order needed (usually until the derivatives become zero or a pattern emerges): - \(f(x) = x^{3} - 2x + 4\) - \(f'(x) = 3x^{2} - 2\) - \(f''(x) = 6x\) - \(f^{(3)}(x) = 6\) - \(f^{(4)}(x) = 0\) (and all higher derivatives are zero).
Evaluate each derivative at \(x = 2\): - \(f(2) = 2^{3} - 2(2) + 4\) - \(f'(2) = 3(2)^{2} - 2\) - \(f''(2) = 6(2)\) - \(f^{(3)}(2) = 6\) - \(f^{(4)}(2) = 0\).
Write the Taylor series expansion using the formula and the evaluated derivatives: \[f(x) = f(2) + \frac{f'(2)}{1!}(x - 2) + \frac{f''(2)}{2!}(x - 2)^{2} + \frac{f^{(3)}(2)}{3!}(x - 2)^{3} + \cdots\] Since higher derivatives are zero, the series will terminate here.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Taylor Series

A Taylor series represents a function as an infinite sum of terms calculated from the derivatives of the function at a single point a. It approximates the function near that point using polynomial terms, where each term involves the nth derivative evaluated at a, multiplied by (x - a)^n and divided by n!.
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Taylor Series

Maclaurin Series

The Maclaurin series is a special case of the Taylor series centered at a = 0. It expresses a function as an infinite sum of derivatives evaluated at zero, useful for approximating functions near zero. Understanding this helps distinguish between general Taylor expansions and those specifically at zero.
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Convergence of Taylor & Maclaurin Series

Derivatives and Their Role in Series Expansion

Derivatives of a function at the point a determine the coefficients of the Taylor series. Calculating successive derivatives and evaluating them at a provides the necessary values to build each term of the series, reflecting the function's behavior near a.
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