Chapter 9: Problem 22
Using a Binomial Series In Exercises \(21-26\) use the binomial series to find the Maclaurin series for the function. $$f(x)=\frac{1}{(1+x)^{4}}$$
Short Answer
Expert verified
The Maclaurin series for the function \(f(x)=\frac{1}{(1+x)^{4}}\) is \(f(x)= \sum_{k=0}^{\infty} \frac{(-1)^k 4.5.6...(3+k)}{k!} x^k \).
Step by step solution
01
Recall the Binomial Series
Invoke the Binomial Theorem or Series which is \( (1+x)^n = \sum_{k=0}^{\infty} \binom{n}{k} x^k \) for \( |x| < 1 \). In this case, \(n\) is negative (-4).
02
Apply the Binomial Series to Function
Replace \(n\) with -4 in the Binomial Series definition, which will give us: \(f(x)= (1+x)^{-4} = \sum_{k=0}^{\infty} \binom{-4}{k} x^k\).
03
Simplify the binomial coefficient
To simplify the function further, we create general term based on the binomial coefficient pattern: \(f(x)= \sum_{k=0}^{\infty} \frac{(-4)(-5)...(-3-k)}{k!} x^k\).
04
Simplification of series terms
We can further simplify the series terms, leading to: \(f(x)= \sum_{k=0}^{\infty} \frac{(-4)(-5)...(-3-k)}{k!} x^k = \sum_{k=0}^{\infty} \frac{(-1)^k 4.5.6...(3+k)}{k!} x^k \).
05
Identify the Maclaurin Series
Maclaurin series is simply a Taylor series centered at 0. The general form of a Maclaurin series is \(f(x) = \sum_{n=0}^\infty \frac{f^n(0)}{n!} x^n \). Comparing this with the Binomial series identified earlier, the Maclaurin series corresponding to the given function is \(f(x)= \sum_{k=0}^{\infty} \frac{(-1)^k 4.5.6...(3+k)}{k!} x^k \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Series
The binomial series is a special type of power series that expands expressions of the form \((1 + x)^n\). This series is especially useful when \(n\) is not a positive integer, allowing it to handle cases with negative or fractional exponents. The general form of the binomial series is: \[(1 + x)^n = \sum_{k=0}^{\infty} \binom{n}{k} x^k\]where \(\binom{n}{k}\) represents the binomial coefficient.
- The series converges for \(|x| < 1\).
- It can be used to approximate functions in terms of polynomials.
- When \(n\) is a negative integer or a fraction, the expansion can be infinite.
Binomial Theorem
The binomial theorem provides a formula for expanding expressions raised to a power. It primarily applies to positive integer exponents, yet it serves as the foundation for understanding the binomial series. The theorem states that:\[(1 + x)^n = \sum_{k=0}^{n} \binom{n}{k} x^k\]where \(n\) is a non-negative integer. This differs from the binomial series by having a finite number of terms when \(n\) is a whole number.Key aspects include:
- \(\binom{n}{k}\) is the number of ways to choose \(k\) elements from \(n\) and is called a binomial coefficient.
- The coefficients correspond to those found in Pascal's Triangle, a useful tool for calculating smaller values.
- The binomial theorem simplifies calculations in cases where expansion is possible.
Taylor Series
A Taylor series represents a function as an infinite sum of terms calculated from the values of its derivatives at a single point. Its versatility makes it a powerful tool in mathematical analysis. For a function \(f(x)\), the Taylor series centered around a point \(a\) is given by:\[f(x) = \sum_{n=0}^{\infty} \frac{f^n(a)}{n!} (x-a)^n\]where \(f^n(a)\) is the \(n\)-th derivative of \(f\) evaluated at \(a\).Important points include:
- The Taylor series allows for the approximation of functions through polynomial expressions.
- It converges to the function as more terms are added, typically within a specific range.
- It is crucial for understanding approximation techniques in engineering, physics, and other sciences.
Series Expansion
Series expansion involves expressing a mathematical function as an infinite sum of terms defined by a specific rule or pattern. This technique is integral in analyzing functions within a wide range of applications.
Some key characteristics include:
- Series expansions simplify complex functions into more manageable polynomial forms.
- They help in approximating functions that are difficult to compute directly.
- Applications range from solving differential equations to modeling physical systems.