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Ch. 4 - Applications of the Derivative
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243당신이 사용하는 게 아니라요?교과서 변경
4장, 문제 89

More limits Evaluate the following limits.
lim_x→1 (x ln x - x + 1) / (xln²x)

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First, identify the form of the limit as x approaches 1. Substitute x = 1 into the expression (x ln x - x + 1) / (x ln²x) to check if it results in an indeterminate form like 0/0.
Since substituting x = 1 results in an indeterminate form, apply L'Hôpital's Rule, which is used to evaluate limits of indeterminate forms. This rule states that if the limit of f(x)/g(x) as x approaches a value results in 0/0 or ∞/∞, then it can be evaluated as the limit of f'(x)/g'(x).
Differentiate the numerator f(x) = x ln x - x + 1 with respect to x. Use the product rule for the term x ln x, which gives the derivative as ln x + 1. The derivative of -x is -1, and the derivative of the constant 1 is 0.
Differentiate the denominator g(x) = x ln²x with respect to x. Again, use the product rule. The derivative of x is 1, and the derivative of ln²x is 2 ln x * (1/x) by the chain rule. Combine these to get the derivative of the denominator.
Substitute the derivatives back into the limit expression and evaluate the new limit as x approaches 1. If necessary, apply L'Hôpital's Rule again if the result is still an indeterminate form.

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주요 개념

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

Limits

Limits are fundamental in calculus, representing the value that a function approaches as the input approaches a certain point. They are essential for understanding continuity, derivatives, and integrals. In this context, evaluating the limit as x approaches 1 involves analyzing the behavior of the function near that point, which may require techniques like substitution or L'Hôpital's rule if the limit results in an indeterminate form.
추천 영상:
05:50
One-Sided Limits

Indeterminate Forms

Indeterminate forms occur when direct substitution in a limit leads to expressions like 0/0 or ∞/∞, which do not provide clear information about the limit's value. Recognizing these forms is crucial for applying methods such as L'Hôpital's rule, which allows for differentiation of the numerator and denominator to resolve the limit. In the given limit, substituting x = 1 results in an indeterminate form, necessitating further analysis.
추천 영상:
3:56
Slope-Intercept Form

L'Hôpital's Rule

L'Hôpital's Rule is a powerful tool in calculus used to evaluate limits that result in indeterminate forms. It states that if the limit of f(x)/g(x) as x approaches a point yields 0/0 or ∞/∞, then the limit can be found by taking the derivative of the numerator and the derivative of the denominator. This rule simplifies the evaluation process, making it easier to find the limit of complex functions like the one presented in the question.
추천 영상:
5:50
Power Rules