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Ch. 5 - Systems of Equations and Inequalities
Blitzer - College Algebra 8th Edition
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Capitolo 6, Problema 24

In Exercises 16–24, write the partial fraction decomposition of each rational expression. (4x^3 + 5x^2 + 7x - 1)/(x^2 + x + 1)^2

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Step 1: Recognize that the given rational expression is a proper fraction, as the degree of the numerator (4x^3 + 5x^2 + 7x - 1) is less than the degree of the denominator ((x^2 + x + 1)^2). This means partial fraction decomposition is applicable.
Step 2: Factor the denominator if possible. In this case, the denominator is already expressed as (x^2 + x + 1)^2, which is a repeated irreducible quadratic factor.
Step 3: Set up the partial fraction decomposition. For a repeated irreducible quadratic factor like (x^2 + x + 1)^2, the decomposition will take the form: A(x) / (x^2 + x + 1) + B(x) / (x^2 + x + 1)^2, where A(x) and B(x) are polynomials of degree less than the degree of the quadratic factor (degree < 2). Thus, A(x) = Ax + B and B(x) = Cx + D.
Step 4: Write the equation for the decomposition: (4x^3 + 5x^2 + 7x - 1) / (x^2 + x + 1)^2 = (Ax + B) / (x^2 + x + 1) + (Cx + D) / (x^2 + x + 1)^2.
Step 5: Multiply through by the denominator (x^2 + x + 1)^2 to eliminate the fractions, resulting in: 4x^3 + 5x^2 + 7x - 1 = (Ax + B)(x^2 + x + 1) + (Cx + D). Expand and collect like terms, then equate coefficients of corresponding powers of x to solve for A, B, C, and D.

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