Chapter 4: Problem 48
In Problems \(48-50,\) evaluate the limit using the fact that $$\lim _{n \rightarrow \infty}\left(1+\frac{1}{n}\right)^{n}=e$$ $$\lim _{x \rightarrow 0^{+}}(1+x)^{1 / x}$$
Short Answer
Expert verified
The limit is \( e \).
Step by step solution
01
Understand the Problem
We are asked to evaluate the limit \( \lim _{x \rightarrow 0^{+}}(1+x)^{1 / x} \). It is important to recognize that this expression takes a form similar to the known limit \( \lim _{n \to \infty}\left(1+\frac{1}{n}\right)^{n}=e \).
02
Substitute Variable
To make the expression fit the form \(\left(1+\frac{1}{n}\right)^{n}=e\), let \(y = \frac{1}{x}\). As \(x\) approaches \(0^{+}\), \(y\) approaches \(\infty\).
03
Rewrite the Expression
Rewrite the original limit using the substitution: \( \lim_{x \to 0^{+}} (1 + x)^{1/x} \) becomes \( \lim_{y \to \infty} (1 + 1/y)^{y} \).
04
Apply Known Limit Result
Recognize the expression \( \lim_{y \to \infty} (1 + 1/y)^{y} \) as directly matching the known form \( \lim _{n \rightarrow \infty}\left(1+\frac{1}{n}\right)^{n} = e \). Thus, the limit evaluates to \( e \).
05
Conclusion
Since the rewritten expression directly matches the well-established limit, we conclude that\[ \lim _{x \rightarrow 0^{+}}(1+x)^{1 / x} = e. \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Limit Evaluation
Evaluating limits is a fundamental process in calculus. It involves finding the value that a function approaches as the variable tends toward a particular point or infinity. In the problem given, the function to evaluate is \( \lim _{x \rightarrow 0^{+}}(1+x)^{1 / x} \). Understanding limit evaluation begins with recognizing how the expression behaves as \( x \) approaches the specified condition.
- First, identify the form of the limit, as it may resemble standard forms you know.
- Next, apply well-known results or rules to simplify the expression.
- Lastly, ensure the transformation is valid under the limit’s conditions.
Variable Substitution
Variable substitution is a helpful method to simplify limits by transforming expressions into familiar forms. In this problem, we begin by setting \( y = \frac{1}{x} \). This substitution dramatically simplifies our work. Here’s how it helps:When you substitute variables, keep in mind the direction and the value where the original variable tends.
- As \( x \to 0^{+} \), the substitution means \( y \to \infty \).
- This change alters the original limit \( \lim_{x \to 0^{+}} (1 + x)^{1/x} \) to \( \lim_{y \to \infty} (1 + 1/y)^{y} \).
- This substitution converts the tricky expression into a familiar one that matches a well-known pattern.
Exponential Limit
The concept of exponential limits is embedded deeply within calculus, particularly when exploring growth patterns and continuous compounding. The expression \( \lim _{n \rightarrow \infty}(1+\frac{1}{n})^{n} = e \) is a cornerstone in this area.The given problem pivots around this known exponential limit.
- By using the substitution \( y = \frac{1}{x} \), the expression becomes \( \lim_{y \to \infty} (1 + 1/y)^{y} \).
- This is exactly the structure of the exponential limit that evaluates to \( e \).
- The substitution illustrates how seemingly different limits relate to exponential growth concepts, leveraging existing knowledge for quick evaluation.