Chapter 2: Problem 28
Determine the infinite limit. $$\lim _{x \rightarrow 5^{-}} \frac{e^{x}}{(x-5)^{3}}$$
Short Answer
Expert verified
The limit is \(-\infty\).
Step by step solution
01
Analyze the Type of Limit
The expression involves a limit as \( x \) approaches 5 from the left. The denominator \( (x-5)^3 \) becomes very small, more precisely approaching zero from the negative side because we approach from the left \( (x \to 5^-) \). This pushes the fraction towards an infinite limit since division by zero tends to infinity.
02
Behavior of the Numerator
As \( x \) approaches 5, \( e^x \) is continuous and approaches \( e^5 \), a positive finite number. The exponential function is smooth and increasing, meaning \( e^x \) remains positive approaching \( e^5 \).
03
Behavior of the Denominator
The cube \( (x-5)^3 \) goes towards zero from the negative side because of the \( x o 5^- \). The cube essentially remains negative but very small in magnitude.
04
Evaluating the Limit
Combine observations: the numerator remains positive while the denominator approaches a negative small value, hence the fraction as a whole tends towards \( -\infty \) because a positive number divided by a negative number (tending to zero magnitude) will be a large negative number.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Left-Hand Limit
When dealing with limits, the notation specifically influences how we approach a particular value. The left-hand limit refers to the values approached as we come from the left side of a specific point. In mathematical terms, if we take the limit \[ \lim_{x \to a^-} f(x) \]we mean we are observing the behavior of the function as the value of \( x \) approaches \( a \) from values smaller than \( a \). This is an important distinction because the behavior of the function can vastly differ when approached from different directions. For instance, in our exercise,- \( x \to 5^- \) means that \( x \) is approaching 5 from values less than 5, indicating we consider smaller increments from 4.9, 4.99, etc.- Analyzing limits from just one direction helps capture any possible asymmetrical behavior in the function.
Asymptotic Behavior
Asymptotic behavior describes how a function behaves as the independent variable approaches a certain point or even infinity. In calculus, as \( x \) gets closer and closer to a certain value, the function might still climb higher or lower without bound. In our example, we are interested in how the function behaves as \( x \) approaches 5 from the left:
- The behavior is termed "asymptotic" because the graph of \( \frac{e^{x}}{(x-5)^{3}} \) will get infinitely close to a vertical line at \( x = 5 \).
- Such an asymptote indicates that the function may grow to be extremely large in the positive or negative direction.
Exponential Function
The exponential function, denoted as \( e^{x} \), is a fundamental component in calculus and mathematical analysis. It is characterized by its constant rate of growth, which is unique and unmatched by any polynomial or linear function:
- For any value of \( x \), the function \( e^{x} \) remains positive and smooth, meaning its curve never dips below the x-axis.
- As \( x \) increases, \( e^{x} \) grows exponentially. However, even in small intervals around a particular point, the function maintains its continuity and positivity.
Division by Zero
Division by zero is a concept that is fundamentally undefined in mathematics, due to the nature of division requiring a non-zero divisor for meaningful results. When a denominator approaches zero, as noted in our problem with \( (x-5)^{3} \):
- From the left, \( x \to 5^- \), makes \( (x-5)^3 \) approach a negative, very small number (close to zero).
- This results in a scenario where dividing by this quantity causes the value to blow up negatively, essentially leading towards \(-\infty\).