Chapter 1: Problem 34
Find the limits. $$ \lim _{x \rightarrow+\infty} \frac{1-e^{x}}{1+e^{x}} $$
Short Answer
Expert verified
The limit is -1.
Step by step solution
01
Understanding the Limit
We need to find the limit of the function \( \frac{1-e^{x}}{1+e^{x}} \) as \( x \to +\infty \). This means we evaluate what happens to the expression as \( x \) becomes very large.
02
Analyzing the Exponential Growth
As \( x \to +\infty \), the term \( e^{x} \) dominates both the numerator and the denominator due to its exponential growth. Therefore, it is important to focus on how \( e^x \) affects the entire fraction.
03
Factor out \( e^x \)
To simplify the expression, factor \( e^x \) from both the numerator and the denominator: \[ \frac{1-e^{x}}{1+e^{x}} = \frac{\frac{1}{e^{x}} - 1}{\frac{1}{e^{x}} + 1}. \] This manipulation helps to see the behavior as \( x \) approaches infinity.
04
Evaluate the Simplified Expression
As \( x \to +\infty \), the term \( \frac{1}{e^x} \to 0 \) because the exponential in the denominator grows without bounds. The expression now becomes:\[ \frac{0 - 1}{0 + 1} = -1. \]
05
Determine the Limit
With the simplified expression, we find that the limit as \( x \to +\infty \) is\[ \lim_{x \to +\infty} \frac{1-e^{x}}{1+e^{x}} = -1. \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Exponential Growth
Exponential growth occurs when the rate of change of a quantity is proportional to its current amount. This is characterized by the function \( e^x \), where \( e \) is the base of the natural logarithm, approximately equal to 2.718. In the context of limits, exponential functions often demonstrate dramatic increases as \( x \) approaches infinity.
As \( x \) grows larger and larger, the value of \( e^x \) becomes significantly large, dominating other terms in the expression. This characteristic makes exponential functions particularly important when analyzing expressions at the limits, especially as \( x \) approaches infinity. Because of the sharp increase in growth with larger \( x \), such terms typically overpower constants or lower degree polynomial terms, which is crucial for understanding limit behavior.
As \( x \) grows larger and larger, the value of \( e^x \) becomes significantly large, dominating other terms in the expression. This characteristic makes exponential functions particularly important when analyzing expressions at the limits, especially as \( x \) approaches infinity. Because of the sharp increase in growth with larger \( x \), such terms typically overpower constants or lower degree polynomial terms, which is crucial for understanding limit behavior.
- Exponential functions grow faster than any polynomial function of \( x \).
- For very large values of \( x \), terms like \( 1 - e^x \) and \( 1 + e^x \) are heavily influenced by \( e^x \).
The Technique of Factorization
Factorization is a mathematical process that involves breaking down an expression into a product of simpler expressions. In limit problems, factorization helps simplify complex expressions into more manageable forms. In our exercise, we factor out \( e^x \) from both the numerator and the denominator to simplify the problem.
The original expression \( \frac{1-e^{x}}{1+e^{x}} \) can be rewritten by recognizing \( e^x \) as a common factor dominating the terms. By dividing every term by \( e^x \), the expression becomes \( \frac{\frac{1}{e^x} - 1}{\frac{1}{e^x} + 1} \).
The original expression \( \frac{1-e^{x}}{1+e^{x}} \) can be rewritten by recognizing \( e^x \) as a common factor dominating the terms. By dividing every term by \( e^x \), the expression becomes \( \frac{\frac{1}{e^x} - 1}{\frac{1}{e^x} + 1} \).
- Factorization highlights the dominant term, simplifying the problem.
- This practice is invaluable in limits as it reveals behavior for extreme values of \( x \).
Infinity Behavior in Limits
Understanding how functions behave as they approach infinity is crucial in calculus, particularly when evaluating limits. In our exercise, the behavior of \( \frac{1-e^{x}}{1+e^{x}} \) as \( x \to +\infty \) needs to be examined closely.
As \( x \) goes to infinity, we see the exponential term \( e^x \) growing tremendously, making \( \frac{1}{e^x} \) tend towards zero. Because of this, the simplified expression \( \frac{\frac{1}{e^x} - 1}{\frac{1}{e^x} + 1} \) becomes \( \frac{0 - 1}{0 + 1} \), which equals \(-1\).
As \( x \) goes to infinity, we see the exponential term \( e^x \) growing tremendously, making \( \frac{1}{e^x} \) tend towards zero. Because of this, the simplified expression \( \frac{\frac{1}{e^x} - 1}{\frac{1}{e^x} + 1} \) becomes \( \frac{0 - 1}{0 + 1} \), which equals \(-1\).
- Recognizing the magnitude and effect of \( e^x \) allows us to ascertain the impact on limit assessments.
- The main effect of approaching infinity led to ignoring the \( \frac{1}{e^x} \) term completely.