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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 8.5.6

Expand the quotients in Exercises 1–8 by partial fractions.
z / (z³ - z² - 6z)

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Start by factoring the denominator of the given expression \(\frac{z}{z^{3} - z^{2} - 6z}\). First, factor out the common factor \(z\): \(z^{3} - z^{2} - 6z = z(z^{2} - z - 6)\).
Next, factor the quadratic expression \(z^{2} - z - 6\). Find two numbers that multiply to \(-6\) and add to \(-1\). These numbers are \(-3\) and \(2\), so: \(z^{2} - z - 6 = (z - 3)(z + 2)\).
Rewrite the original expression using the factored denominator: \(\frac{z}{z(z - 3)(z + 2)}\).
Set up the partial fraction decomposition. Since the denominator factors are linear and distinct, express the fraction as: \(\frac{z}{z(z - 3)(z + 2)} = \frac{A}{z} + \frac{B}{z - 3} + \frac{C}{z + 2}\), where \(A\), \(B\), and \(C\) are constants to be determined.
Multiply both sides of the equation by the common denominator \(z(z - 3)(z + 2)\) to clear the denominators: \(z = A(z - 3)(z + 2) + B z (z + 2) + C z (z - 3)\). This equation can now be expanded and simplified to solve for \(A\), \(B\), and \(C\) by equating coefficients or substituting convenient values of \(z\).

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