Chapter 8: Problem 43
Graph \(y=x^{1 / x}\) for \(x>0 .\) Show what happens for very small \(x\) and very large \(x\). Indicate the maximum value.
Short Answer
Expert verified
The maximum value of the function \( y = x^{1/x} \) occurs at \( x = e \) and is \( y = e^{1/e} \approx 1.445 \).
Step by step solution
01
Understanding the Function
The function given is \( y = x^{1/x} \). This means for each \( x \), we take the \( x \)-th root of \( x \). We need to understand how this behaves as \( x \) approaches small and large values.
02
Analyzing the Behavior for Small x
For very small values of \( x \) (close to 0 but positive), \( x^{1/x} \) behaves peculiarly. As \( x \to 0^+ \), \( y = x^{1/x} \) approaches 0 because the exponent \( 1/x \) becomes very large, leading to the base \( x \) becoming very small.
03
Analyzing the Behavior for Large x
For very large values of \( x \), the function \( x^{1/x} \) approaches 1. As \( x \to \infty \), the exponent \( 1/x \) approaches 0, which makes \( x^{1/x} \to e^0 = 1 \).
04
Finding the Critical Point
To find the maximum value, we take the derivative of \( y = x^{1/x} \). Rewriting the function as \( y = e^{(\ln x)/x} \), differentiate to find critical points. Set the derivative to zero to find \( x = e \), where \( y \) reaches a maximum value.
05
Calculating the Maximum Value
At \( x = e \), we calculate \( y = e^{1/e} \). This is the maximum value of the function. Numerically, it approximates to about \( 1.444667861 \).
06
Graphing the Function
Plotting the function for \( x > 0 \), you should see it starts from zero at \( x = 0 \), rises to \( 1.444667861 \) at \( x = e \), and then gradually decreases towards 1. This shows the increasing then decreasing nature of the function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Behavior
Understanding how a function behaves for various values of its variable is essential for graphing. Let's break it down for the function \( y = x^{1/x} \).
As x gets very small (close to 0 but still positive):
As x becomes very large:
By considering both extremes, we can visualize the trend of the function as a rise to a peak before settling towards 1.
As x gets very small (close to 0 but still positive):
- The term \( 1/x \) becomes very large.
- The base \( x \) becomes very small.
As x becomes very large:
- The term \( 1/x \) gets closer to zero.
- Thus the exponent approaches zero.
By considering both extremes, we can visualize the trend of the function as a rise to a peak before settling towards 1.
Critical Points
Critical points are where the function's derivative equals zero or fails to exist, potentially indicating maximum or minimum values.
For \( y = x^{1/x} \), we locate the critical point to find where the function peaks. Derivative analysis helps us here. By rewriting \( y \) as \( e^{(\ln x)/x} \), differentiation becomes manageable.
The derivative is set to zero:
For \( y = x^{1/x} \), we locate the critical point to find where the function peaks. Derivative analysis helps us here. By rewriting \( y \) as \( e^{(\ln x)/x} \), differentiation becomes manageable.
The derivative is set to zero:
- Solving the derivative provides critical points—here at \( x = e \).
- This value signifies where the function reaches its highest point before decreasing.
Derivative Analysis
Derivatives help us understand the rate of change of functions and find critical points.
For \( y = x^{1/x} \), we express it as \( y = e^{(\ln x)/x} \) to use differentiation efficiently.
Taking the derivative involves applying the chain rule and results in:
For \( y = x^{1/x} \), we express it as \( y = e^{(\ln x)/x} \) to use differentiation efficiently.
Taking the derivative involves applying the chain rule and results in:
- The derivative equals zero at \( x = e \), indicating a peak or valley.
- Differentiate to understand not just when, but how, the function changes around that point.