Chapter 10: Problem 13
Find the Maclaurin series for the functions \(\frac{1}{1+x}\)
Short Answer
Expert verified
The Maclaurin series is \(1 - x + x^2 - x^3 + \ldots = \sum_{n=0}^{\infty} (-1)^n x^n\).
Step by step solution
01
Understanding the Maclaurin Series
The Maclaurin series is a special case of the Taylor series, where the expansion of the function is performed at the point \(x = 0\). The Maclaurin series for a function \(f(x)\) is given by the formula: \[f(x) = f(0) + f'(0)x + \frac{f''(0)}{2!}x^2 + \frac{f'''(0)}{3!}x^3 + \ldots\]
02
Identify the Function and its Derivatives
We have the function \(f(x) = \frac{1}{1+x}\). Let's compute its derivatives at \(x = 0\) to use them in the series expansion. First, compute \(f(0)\): - \(f(x) = \frac{1}{1+x}\) so \(f(0) = \frac{1}{1+0} = 1\). Next, compute the first few derivatives:- First derivative: \(f'(x) = -\frac{1}{(1+x)^2}\), so \(f'(0) = -1\).- Second derivative: \(f''(x) = \frac{2}{(1+x)^3}\), so \(f''(0) = 2\).- Third derivative: \(f'''(x) = -\frac{6}{(1+x)^4}\), so \(f'''(0) = -6\).
03
Construct the Maclaurin Series
Using the derivatives calculated at \(x = 0\), we construct the Maclaurin Series:\[f(x) = 1 - x + \frac{2}{2!}x^2 - \frac{6}{3!}x^3 + \ldots \]This simplifies to:\[f(x) = 1 - x + x^2 - x^3 + \ldots \]
04
Conclude the Pattern of the Series
The pattern of the Maclaurin series for \(\frac{1}{1+x}\) emerges as:\[f(x) = \sum_{n=0}^{\infty} (-1)^n x^n\]This is the series representation, where the coefficient alternates the sign for each successive power of \(x\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Taylor series
The Taylor series is a powerful mathematical tool used to represent functions as infinite sums of derivatives at a single point. This allows us to understand complex functions in simpler terms.
- The Taylor series can be expressed using a formula involving function derivatives at a specific point, often denoted by \(a\).
- The general form of a Taylor series for a function \(f(x)\) centered around \(a\) is: \[ f(x) = f(a) + f'(a)(x-a) + \frac{f''(a)}{2!}(x-a)^2 + \frac{f'''(a)}{3!}(x-a)^3 + \ldots \]
- In the case of a Maclaurin series, which is a special case of the Taylor series, the expansion is done around \(a = 0\).
- This effectively means that the Maclaurin series is just a simplified form of the Taylor series, applicable when the derivatives are evaluated and summed at the origin.
function expansion
Function expansion through series is a way to express a function as an infinite sum of terms calculated from the values of its derivatives at a single point. This approach is crucial in applications like physics, engineering, and other fields where you model systems using mathematical functions.
- Function expansion captures the essence of the function by using polynomial-like structures to approximate the function values over an interval.
- The Maclaurin series is an example of this, expanding the function \( \frac{1}{1+x} \) into an infinite series: \[ f(x) = 1 - x + x^2 - x^3 + \ldots \]
- Expanding a function allows for easier computation, especially when dealing with complex analytical problems.
- One key advantage is that with Maclaurin series, you can evaluate function values close to zero with higher accuracy and less computational effort.
derivative computation
Computing derivatives is a central task in finding series expansions like the Maclaurin series. Derivatives measure how a function changes as its input changes, providing information needed to construct polynomial approximations.
- For the function \( f(x) = \frac{1}{1+x} \), knowing the first few derivatives and their values at \( x = 0 \) is necessary for its Maclaurin series.
- The derivatives computed are as follows:
- First derivative: \( f'(x) = -\frac{1}{(1+x)^2} \)
- Second derivative: \( f''(x) = \frac{2}{(1+x)^3} \)
- Third derivative: \( f'''(x) = -\frac{6}{(1+x)^4} \)
- Evaluating these at \( x = 0 \) determines their contribution to the Maclaurin series:
- \( f'(0) = -1 \)
- \( f''(0) = 2 \)
- \( f'''(0) = -6 \)