Chapter 6: Problem 11
Evaluate each limit (or state that it does not exist). $$ \lim _{a \rightarrow-\infty} e^{2 a} $$
Short Answer
Expert verified
The limit is 0.
Step by step solution
01
Understanding the Expression
The limit expression we need to evaluate is \( \lim _{a \rightarrow -\infty} e^{2a} \). This expression contains the exponential function \( e^{2a} \), where the base is the mathematical constant \( e \approx 2.718 \), and the expression inside is \( 2a \). As \( a \) approaches negative infinity, we need to evaluate how \( 2a \) affects the entire expression.
02
Analyzing \( 2a \) as \( a \to -\infty \)
When \( a \rightarrow -\infty \), the expression \( 2a \) also approaches \( -\infty \) because multiplying a negative number (\( a \)) by a positive constant (2) yields a more negative number. Therefore, as \( a \rightarrow -\infty \), \( 2a \rightarrow -\infty \).
03
Evaluating the Exponential Function
The behavior of the exponential function \( e^x \) as \( x \to -\infty \) is critical here. As \( x \to -\infty \), \( e^x \to 0 \). This is because the exponential function decreases rapidly towards zero as its exponent becomes a large negative number.
04
Calculating the Limit
Given the behavior of \( e^x \), when \( x = 2a \) and \( 2a \rightarrow -\infty \), the function \( e^{2a} \rightarrow 0 \). Hence, the limit is \( 0 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Functions
Exponential functions are a fundamental concept in mathematics. These functions have the form \( e^x \), where \( e \) is a constant approximately equal to 2.718, known as Euler's number. This constant is the base of the natural logarithm and plays a critical role in growth processes. Exponential functions are characterized by rapid growth or decay:
For example, when you deal with an exponential function like \( e^{2a} \):
- If the exponent is positive, the function grows rapidly as the variable increases.
- If the exponent is negative, the function decreases rapidly towards zero.
For example, when you deal with an exponential function like \( e^{2a} \):
- As \( a \) increases, \( 2a \) becomes more positive, and \( e^{2a} \) grows large.
- Conversely, when \( a \) turns negative and gets larger in magnitude, \( 2a \) decreases, driving \( e^{2a} \) towards zero.
Infinite Limits
Infinite limits occur when a variable approaches infinity or negative infinity, affecting the overall behavior of a function. As variables approach these extreme values, functions can either shoot towards an infinite value, zero, or sometimes become undefined.
In the context of exponential functions like \( e^{2a} \):
Infinite limits provide valuable insights into how functions behave as their inputs grow without restraint.
In the context of exponential functions like \( e^{2a} \):
- As \( a \to \infty \), the exponent \( 2a \) also tends to infinity, causing \( e^{2a} \) to grow infinitely large.
- Conversely, as \( a \to -\infty \), \( 2a \) also approaches \( -\infty \), which results in the exponential function \( e^{2a} \) tending towards zero.
Infinite limits provide valuable insights into how functions behave as their inputs grow without restraint.
Evaluating Limits
Evaluating limits is a critical skill in calculus, allowing us to understand the behavior of functions at boundaries, especially when direct substitution is not possible. To evaluate a limit:
In the exercise \( \lim_{a \to -\infty} e^{2a} \), observe how the function trends towards zero as \( a \) becomes a larger negative number. This analysis demonstrates a fundamental understanding of limits in the context of exponential decay. Evaluating such limits involves recognizing patterns and utilizing the inherent properties of exponential functions.
- Consider the behavior of the function as the variable approaches a given value.
- For exponential functions, recognize how rapid growth or decay impacts the function's approach to that limit.
In the exercise \( \lim_{a \to -\infty} e^{2a} \), observe how the function trends towards zero as \( a \) becomes a larger negative number. This analysis demonstrates a fundamental understanding of limits in the context of exponential decay. Evaluating such limits involves recognizing patterns and utilizing the inherent properties of exponential functions.