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In Exercises \(1-20\), determine whether the given limit exists. If it does exist, then compute it. $$ \lim _{x \rightarrow+\infty} \frac{\sqrt{x}}{x+1} $$

Short Answer

Expert verified
The limit is 0.

Step by step solution

01

Analyze the Expression

Consider the given limit, which is \( \lim_{x \rightarrow +\infty} \frac{\sqrt{x}}{x+1} \). As \( x \) approaches infinity, both the numerator \( \sqrt{x} \) and the denominator \( x+1 \) grow very large. Our goal is to determine how quickly each part of the fraction grows relative to the other.
02

Simplify Using Leading Terms

To determine the behavior of the fraction at infinity, focus on the leading term of the numerator \( \sqrt{x} \) and the denominator \( x \). For large \( x \), \( x+1 \approx x \), so the fraction simplifies to \( \frac{\sqrt{x}}{x} \).
03

Apply L'Hôpital's Rule If Necessary

If the limit is indeterminate of the form \( \frac{\infty}{\infty} \), we can apply L'Hôpital's Rule by differentiating the numerator and the denominator. However, it's simpler here to express the fraction: \( \frac{\sqrt{x}}{x} = \frac{1}{\sqrt{x}} \).
04

Evaluate the Simplified Limit

As \( x \rightarrow +\infty \), \( \frac{1}{\sqrt{x}} \rightarrow 0 \) because \( \sqrt{x} \) grows without bound, making the fraction smaller and tending to zero.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Indeterminate Forms
In calculus, an indeterminate form is an expression that cannot be determined directly because it lacks a definite value or leads to ambiguity. A common example is the form \( \frac{\infty}{\infty} \), which arises in many limits involving large numbers. When both the numerator and the denominator grow very large, it's unclear what the resulting fraction will approach without further analysis.

To determine what happens with indeterminate forms, mathematicians often look at other methods to simplify the problem. This might include simplifying the expression, as we did by noting \( x+1 \approx x \) for very large \( x \). Understanding that both the numerator, \( \sqrt{x} \), and the denominator, \( x+1 \), tend towards infinity helps us classify the problem as \( \frac{\infty}{\infty} \) and decide whether it's necessary to apply more advanced techniques, such as L'Hôpital's Rule, to find the limit.
  • Indeterminate forms appear frequently in limit problems.
  • They require specific strategies to resolve, like algebraic simplifications or calculus techniques.
  • Recognizing these forms is crucial for correctly computing limits.
L'Hôpital's Rule
L'Hôpital's Rule is an indispensable tool in calculus for dealing with limits that present indeterminate forms. When a limit is found to be in a form like \( \frac{0}{0} \) or \( \frac{\infty}{\infty} \), L'Hôpital's Rule provides a way to evaluate it by differentiating both the numerator and the denominator separately.

In the context of the original exercise, after simplifying the expression to \( \frac{1}{\sqrt{x}} \), it became unnecessary to apply L'Hôpital's Rule since the expression could be evaluated directly. However, it's worth noting that if a problem remains complex, L'Hôpital's Rule can simplify the evaluation process by iteratively applying derivatives until a determinate form is achieved.
  • Useful for indeterminate forms like \( \frac{0}{0} \) and \( \frac{\infty}{\infty} \).
  • Requires differentiating numerator and denominator separately.
  • Transforms complex limit problems into simpler forms.
Asymptotic Analysis
Asymptotic analysis is a technique used to describe the behavior of functions as inputs grow large. This approach is particularly useful in evaluating limits at infinity, like in the exercise above. By focusing on the leading terms, we can infer how a function behaves as \( x \) approaches infinity.

In this exercise, the simplification \( x+1 \approx x \) let us focus on the dominant term in the denominator. By simplifying to \( \frac{\sqrt{x}}{x} \) and then to \( \frac{1}{\sqrt{x}} \), the behavior of the function as \( x \to \infty \) becomes evident: the limit approaches zero.

Asymptotic analysis helps to:
  • Identify dominant terms in expressions.
  • Understand function behavior at extreme values.
  • Simplify complex problems into manageable forms.
It's a key method for understanding how different parts of a function contribute disproportionately to the overall value as inputs grow large.

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