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Ch. 8 - Integration Techniques
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 8.9.47

7–58. Improper integrals Evaluate the following integrals or state that they diverge.
47. ∫ (from 0 to 10) 1/∜(10 - x) dx

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Identify the integral and the function to be integrated: \( \int_0^{10} \frac{1}{\sqrt[4]{10 - x}} \, dx \). Notice that the integrand involves a fourth root in the denominator, which can cause issues near \( x = 10 \).
Check for any points of discontinuity or where the integrand might be undefined within the interval \([0, 10]\). Since \( \sqrt[4]{10 - x} \) becomes zero at \( x = 10 \), the integrand tends to infinity there, indicating an improper integral at the upper limit.
Rewrite the integral as a limit to handle the improper behavior at \( x = 10 \): \[ \lim_{t \to 10^-} \int_0^t \frac{1}{(10 - x)^{1/4}} \, dx \]. This allows us to evaluate the integral up to a point \( t < 10 \) and then take the limit as \( t \) approaches 10 from the left.
Perform a substitution to simplify the integral. Let \( u = 10 - x \), which implies \( du = -dx \). Change the limits accordingly: when \( x = 0 \), \( u = 10 \); when \( x = t \), \( u = 10 - t \). The integral becomes \( \int_{u=10}^{u=10 - t} u^{-1/4} (-du) = \int_{10 - t}^{10} u^{-1/4} \, du \).
Integrate \( u^{-1/4} \) with respect to \( u \) using the power rule for integrals: \( \int u^n \, du = \frac{u^{n+1}}{n+1} + C \), where \( n = -\frac{1}{4} \). After integrating, substitute back the limits \( u = 10 - t \) and \( u = 10 \), then take the limit as \( t \to 10^- \) to determine if the integral converges or diverges.

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