Chapter 2: Problem 33
Each limit represents the derivative of some function \(f\) at some number \(a .\) State such an \(f\) and \(a\) in each case. $$ \lim _{x \rightarrow 5} \frac{2^{x}-32}{x-5} $$
Short Answer
Expert verified
Function: \( f(x) = 2^{x} \), Point: \( a = 5 \).
Step by step solution
01
Identify the Limit as a Derivative
The given limit \( \lim_{x \rightarrow 5} \frac{2^{x} - 32}{x-5} \) is of the form \( \lim_{x \rightarrow a} \frac{f(x) - f(a)}{x-a} \), which is the definition of the derivative \( f'(a) \). To solve this, we need to identify the function \( f(x) \) and the point \( a \).
02
Determine the Function \( f(x) \)
By examining the difference quotient \( \frac{2^{x} - 32}{x-5} \), observe that \( 2^{x} \) is the term present in the numerator. Therefore, \( f(x) = 2^{x} \).
03
Identify the Value of \( a \)
The term \( x - 5 \) in the denominator indicates that \( a = 5 \). This is the point at which the derivative is being evaluated.
04
Verify \( f(a) \)
Substitute \( x = a = 5 \) into the function \( f(x) \):\[ f(5) = 2^{5} = 32. \] The limit confirms this choice because it simplifies the expression in the numerator \( 2^x - 32 \) to match \( f(x) - f(a) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Derivatives
Derivatives are a fundamental concept in calculus that measure how a function changes as its input changes. Essentially, the derivative represents the rate of change or the slope of a function at a given point. In mathematical terms, if you have a function \( f(x) \), then the derivative at a point \( a \) is given by the expression:\[ f'(a) = \lim_{x \rightarrow a} \frac{f(x) - f(a)}{x-a} \]This expression is known as the difference quotient.
Understanding derivatives fully requires grasping the subtle shifts in the function's behavior, especially recognizing instantaneous rates as opposed to average rates.
- The numerator \( f(x) - f(a) \) represents the change in the function's value.
- The denominator \( x-a \) signifies the change in the input or the "distance" between points on the x-axis.
Understanding derivatives fully requires grasping the subtle shifts in the function's behavior, especially recognizing instantaneous rates as opposed to average rates.
Limits
Limits play a crucial role in calculus, essentially laying the groundwork for defining derivatives and integrals. A limit describes the value that a function (or sequence) approaches as the input approaches some value. Limits are written in the form:\[ \lim_{x \to a} f(x) = L \]Where \( L \) is the value the function \( f \) approaches as \( x \) closes in on \( a \).In our exercise, the limit captures the behavior of the function around the point where \( x \) approaches 5:\[ \lim_{x \rightarrow 5} \frac{2^{x} - 32}{x-5} \]This indicates that the function is approaching a specific value, which is related to its derivative at that point.
- Limits help determine the continuity of a function, establishing whether you can smoothly move through all values.
- They are also used to handle points where direct substitution isn't possible, particularly when the function forms an indeterminate expression like \( \frac{0}{0} \).
Exponential Functions
Exponential functions are defined by their constant rate of growth or decay, typically written in the form \( f(x) = a^{x} \), where \( a \) is a positive constant. In calculus, exponential functions are vital due to their distinctive growing or shrinking patterns, especially in real-world scenarios like population dynamics and financial predictions.
A key property of exponential functions, such as \( 2^x \) from our exercise, is that they grow by a constant ratio. This forms a stepping stone to understanding compounding, such as compound interest in finance.The interest in exponential functions in calculus extends to solving the derivative:
A key property of exponential functions, such as \( 2^x \) from our exercise, is that they grow by a constant ratio. This forms a stepping stone to understanding compounding, such as compound interest in finance.The interest in exponential functions in calculus extends to solving the derivative:
- Exponential functions often result in real-world phenomena that are modeled as rapidly increasing or decreasing.
- When differentiating an exponential function, the derivative often ties back to the original function. For instance, for \( f(x) = a^x \), the derivative can be expressed as \( f'(x) = a^x \ln(a) \).