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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077당신이 사용하는 게 아니라요?교과서 변경
8장, 문제 8.8.66

In Exercises 35–68, use integration, the Direct Comparison Test, or the Limit Comparison Test to test the integrals for convergence. If more than one method applies, use whatever method you prefer.
∫ from 1 to ∞ of ((1 / (e^x - 2^x)) dx)

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1
First, identify the integral to be tested for convergence: \(\displaystyle \int_1^{\infty} \frac{1}{e^x - 2^x} \, dx\).
Examine the behavior of the integrand as \(x \to \infty\). Since both \(e^x\) and \$2^x$ grow exponentially, compare their growth rates to understand the dominant term in the denominator.
Determine which function grows faster: \(e^x\) or \$2^x\(. Recall that \(e \approx 2.718\), so \)e^x\( grows faster than \)2^x\(. Therefore, for large \)x\(, \)e^x - 2^x\( behaves approximately like \)e^x$.
Use the Direct Comparison Test by comparing the integrand to a simpler function that behaves like \(\frac{1}{e^x}\) for large \(x\). Since \(\frac{1}{e^x}\) is a convergent integral on \([1, \infty)\), this comparison can help determine convergence.
Alternatively, apply the Limit Comparison Test by computing the limit \(\displaystyle \lim_{x \to \infty} \frac{\frac{1}{e^x - 2^x}}{\frac{1}{e^x}}\) to confirm if the integrals behave similarly at infinity, which will indicate whether the original integral converges or diverges.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Improper Integrals and Convergence

Improper integrals involve integration over infinite intervals or integrands with infinite discontinuities. To determine convergence, we evaluate the limit of the integral as the upper bound approaches infinity. If this limit exists and is finite, the integral converges; otherwise, it diverges.
추천 영상:
11:11
Improper Integrals: Infinite Intervals

Direct Comparison Test

The Direct Comparison Test compares the given integral's integrand to a simpler function whose convergence behavior is known. If the integrand is less than or equal to a convergent function, the integral converges; if it is greater than or equal to a divergent function, the integral diverges.
추천 영상:
09:25
Direct Comparison Test

Limit Comparison Test

The Limit Comparison Test uses the limit of the ratio of the given integrand to a known function as x approaches infinity. If the limit is a positive finite number, both integrals either converge or diverge together, helping to determine the behavior of complex integrals.
추천 영상:
07:45
Limit Comparison Test