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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 8, Problem 8.PE.26

Evaluate the integrals in Exercises 9–28. It may be necessary to use a substitution first.
∫ [1 / (x (1 + ∛x))] dx

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1
Start by examining the integral \( \int \frac{1}{x (1 + \sqrt[3]{x})} \, dx \). Notice the presence of \( \sqrt[3]{x} \), which suggests a substitution involving \( x^{1/3} \).
Let \( t = \sqrt[3]{x} = x^{1/3} \). Then, express \( x \) in terms of \( t \): \( x = t^3 \).
Differentiate \( x = t^3 \) with respect to \( t \) to find \( dx \): \( dx = 3t^2 \, dt \).
Rewrite the integral in terms of \( t \) by substituting \( x = t^3 \), \( dx = 3t^2 \, dt \), and \( \sqrt[3]{x} = t \). The integral becomes \( \int \frac{1}{t^3 (1 + t)} \cdot 3t^2 \, dt \).
Simplify the integrand: \( \frac{3t^2}{t^3 (1 + t)} = \frac{3}{t (1 + t)} \). Now, the integral is \( \int \frac{3}{t (1 + t)} \, dt \). To integrate, use partial fraction decomposition on \( \frac{1}{t (1 + t)} \) and then integrate term-by-term.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Integration by Substitution

Integration by substitution is a method used to simplify integrals by changing variables. It involves identifying a part of the integrand as a new variable, which transforms the integral into a simpler form. This technique is especially useful when the integral contains composite functions or roots.
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Properties of Exponents and Roots

Understanding how to manipulate exponents and roots is essential for rewriting expressions like ∛x (the cube root of x) as x^(1/3). This allows for easier algebraic manipulation and substitution during integration, enabling the integral to be expressed in terms of powers of x.
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Properties of Functions

Integration of Rational Functions

Integrating rational functions involves integrating ratios of polynomials or expressions that can be transformed into such ratios. Techniques include partial fraction decomposition or substitution to simplify the integrand, making it easier to find the antiderivative.
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