In Exercises 5–18, solve each system by the substitution method.
Ch. 5 - Systems of Equations and Inequalities

Chapter 6, Problem 7
Write the form of the partial fraction decomposition of the rational expression. It is not necessary to solve for the constants.
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Identify the rational expression given: \(\frac{x^3 + x^2}{(x^2 + 4)^2}\).
Recognize that the denominator is a repeated irreducible quadratic factor: \((x^2 + 4)^2\).
For a repeated irreducible quadratic factor \((ax^2 + bx + c)^n\), the partial fraction decomposition includes terms of the form \(\frac{Bx + C}{ax^2 + bx + c}\), \(\frac{Dx + E}{(ax^2 + bx + c)^2}\), and so on, up to the power \(n\).
Write the general form of the partial fraction decomposition for this problem as: \(\frac{Bx + C}{x^2 + 4} + \frac{Dx + E}{(x^2 + 4)^2}\), where \(B\), \(C\), \(D\), and \(E\) are constants to be determined.
Note that since the numerator degree is less than the denominator degree, no polynomial division is necessary before setting up the partial fractions.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Partial Fraction Decomposition
Partial fraction decomposition is a method used to express a rational function as a sum of simpler fractions, making integration or other operations easier. It involves breaking down a complex rational expression into a sum of fractions with simpler denominators, typically linear or irreducible quadratic factors.
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Repeated Quadratic Factors
When the denominator contains a repeated irreducible quadratic factor, such as (x² + 4)², the decomposition includes terms with the quadratic factor raised to each power up to its multiplicity. For example, terms with denominators (x² + 4) and (x² + 4)² appear, each with linear numerators.
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Form of Numerators in Partial Fractions
For linear factors, numerators are constants; for irreducible quadratic factors, numerators are linear expressions (ax + b). This ensures the decomposition can represent any polynomial numerator of lower degree than the denominator factor, allowing for a complete and accurate breakdown.
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A chemist needs to mix a solution that is 34% silver nitrate with one that is 4% silver nitrate to obtain 100 milliliters of a mixture that is 7% silver nitrate. How many milliliters of each of the solutions must be used?
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In Exercises 1–18, solve each system by the substitution method.
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Solve each system in Exercises 5–18.
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An objective function and a system of linear inequalities representing constraints are given. a. Graph the system of inequalities representing the constraints. b. Find the value of the objective function at each corner of the graphed region. c. Use the values in part (b) to determine the maximum value of the objective function and the values of x and y for which the maximum occurs.
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