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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 10.10.1

Find the first four nonzero terms of the Taylor series for the functions in Exercises 1–10.
6. (1 - x/3)^4

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1
Identify the function given: \(f(x) = \left(1 - \frac{x}{3}\right)^4\) and recognize that it is a binomial expression raised to a power.
Recall the Binomial Theorem for expanding \((1 + u)^n\(, which states: \[(1 + u)^n = \sum_{k=0}^{n} \binom{n}{k} u^k,\] where \)\binom{n}{k}\) is the binomial coefficient.
In this problem, set \(u = -\frac{x}{3}\) and \(n = 4\). Write the expansion as: \[\left(1 - \frac{x}{3}\right)^4 = \sum_{k=0}^4 \binom{4}{k} \left(-\frac{x}{3}\right)^k.\]
Calculate each term of the sum for \(k = 0, 1, 2, 3, 4\) by evaluating the binomial coefficients and powers of \(u\), and simplify each term to express it as a polynomial in \(x\).
Write out the first four nonzero terms explicitly from the expansion, which will form the first four nonzero terms of the Taylor series centered at \(x=0\).

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Key Concepts

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

Taylor Series Expansion

A Taylor series represents a function as an infinite sum of terms calculated from the function's derivatives at a single point, usually around x = 0 (Maclaurin series). It approximates functions using polynomials, where each term involves higher-order derivatives and powers of (x - a).
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Binomial Theorem

The binomial theorem provides a formula to expand expressions of the form (1 + u)^n into a sum involving binomial coefficients. For integer powers, it gives exact polynomial expansions, which is useful for finding terms of (1 - x/3)^4 without computing derivatives.
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Nonzero Terms in Series

When finding the first four nonzero terms of a series, it is important to identify and include only those terms whose coefficients are not zero. This ensures the approximation captures the significant behavior of the function near the expansion point.
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