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Ch. 8 - Integration Techniques
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 8.5.20

17-22. Give the partial fraction decomposition for the following expressions.
20. (x² - 4x + 11) / ((x - 3)(x - 1)(x + 1))

Guida verificata passo dopo passo
1
Identify the form of the partial fraction decomposition. Since the denominator is a product of three distinct linear factors \((x - 3)\), \((x - 1)\), and \((x + 1)\), the decomposition will be of the form: \[\frac{A}{x - 3} + \frac{B}{x - 1} + \frac{C}{x + 1}\]
Write the equation equating the original fraction to the sum of partial fractions: \[\frac{x^{2} - 4x + 11}{(x - 3)(x - 1)(x + 1)} = \frac{A}{x - 3} + \frac{B}{x - 1} + \frac{C}{x + 1}\]
Multiply both sides of the equation by the common denominator \((x - 3)(x - 1)(x + 1)\) to clear the denominators: \[x^{2} - 4x + 11 = A(x - 1)(x + 1) + B(x - 3)(x + 1) + C(x - 3)(x - 1)\]
Expand each product on the right-hand side and combine like terms to express the right side as a polynomial in \(x\): - Expand \(A(x - 1)(x + 1)\) - Expand \(B(x - 3)(x + 1)\) - Expand \(C(x - 3)(x - 1)\) Then combine all terms to get a polynomial in the form $Px^{2} + Qx + R$.
Set the coefficients of corresponding powers of \(x\) on both sides equal to each other to form a system of equations: - Coefficient of \(x^{2}\): Left side equals Right side - Coefficient of \(x\): Left side equals Right side - Constant term: Left side equals Right side Solve this system for \(A\), \(B\), and \(C\).

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Partial Fraction Decomposition

Partial fraction decomposition is a technique used to express a rational function as a sum of simpler fractions with linear or quadratic denominators. This method is especially useful for integrating rational functions or simplifying expressions. The goal is to rewrite the given fraction into a form where each term has a simpler denominator.
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Factoring the Denominator

Factoring the denominator into linear or irreducible quadratic factors is essential before performing partial fraction decomposition. In this problem, the denominator is already factored as (x - 3)(x - 1)(x + 1), which allows us to set up the decomposition with terms corresponding to each linear factor.
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Setting Up and Solving for Coefficients

After expressing the rational function as a sum of fractions with unknown coefficients, you multiply both sides by the common denominator to clear fractions. Then, equate coefficients of corresponding powers of x or substitute convenient x-values to solve for the unknown constants, completing the decomposition.
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