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Ch. 4 - Applications of Derivatives
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 4, Problem 4.7.67

Checking Antiderivative Formulas


Right, or wrong? Give a brief reason why.


∫−15(x + 3)² / (x − 2)⁴ dx = ((x + 3)/(x − 2))³ + C

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1
Identify the given integral: \(\int -15 \frac{(x + 3)^2}{(x - 2)^4} \, dx\) and the proposed antiderivative: \(\left( \frac{x + 3}{x - 2} \right)^3 + C\).
To verify if the proposed antiderivative is correct, differentiate \(\left( \frac{x + 3}{x - 2} \right)^3\) using the chain rule.
Let \(u = \frac{x + 3}{x - 2}\). Then the derivative of \(u^3\) with respect to \(x\) is \(3u^2 \cdot \frac{du}{dx}\).
Find \(\frac{du}{dx}\) by applying the quotient rule: \(\frac{d}{dx} \left( \frac{x + 3}{x - 2} \right) = \frac{(1)(x - 2) - (x + 3)(1)}{(x - 2)^2} = \frac{x - 2 - x - 3}{(x - 2)^2} = \frac{-5}{(x - 2)^2}\).
Combine these results: \(\frac{d}{dx} \left( \frac{x + 3}{x - 2} \right)^3 = 3 \left( \frac{x + 3}{x - 2} \right)^2 \cdot \left( \frac{-5}{(x - 2)^2} \right) = -15 \frac{(x + 3)^2}{(x - 2)^4}\), which matches the integrand, confirming the antiderivative is correct.

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Key Concepts

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

Antiderivative and Indefinite Integration

An antiderivative of a function is another function whose derivative equals the original function. Indefinite integration finds all antiderivatives and includes a constant of integration (C) because differentiation loses constant terms. Verifying an antiderivative involves differentiating the proposed solution and checking if it matches the original integrand.
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Introduction to Indefinite Integrals

Chain Rule and Power Rule in Differentiation

The chain rule is used to differentiate composite functions, applying the derivative of the outer function multiplied by the derivative of the inner function. The power rule states that d/dx[x^n] = n*x^(n-1). Understanding these rules is essential to verify if the given antiderivative is correct by differentiating it properly.
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Algebraic Manipulation of Rational Functions

Rational functions are ratios of polynomials, and simplifying or rewriting them can help in integration or differentiation. Recognizing how to express the integrand and the proposed antiderivative in comparable forms is crucial to verify correctness, especially when powers and sums are involved in numerator and denominator.
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Limits of Rational Functions: Denominator = 0