Chapter 2: Problem 121
Graph each function over the given interval. Visually estimate where any absolute extrema occur. Then use the TABLE feature to refine each estimate. $$f(x)=\frac{3}{4}\left(x^{2}-1\right)^{2 / 3} ; \quad\left[\frac{1}{2}, \infty\right)$$
Short Answer
Expert verified
The absolute minimum occurs at \( x = 1 \), \( f(1) = 0 \); no absolute maximum exists.
Step by step solution
01
Understand the Function
The function given is \( f(x) = \frac{3}{4} (x^2 - 1)^{2/3} \). This is a power function with a fractional exponent, which means that it is continuous for all \( x \) where \( x^2 - 1 \geq 0 \). Thus, the function is defined for \( |x| \geq 1 \). Since the provided interval is \( \left[\frac{1}{2}, \infty\right) \), we will focus on the part of the function that starts from \( x = 1 \).
02
Graph the Function
Plot the function \( f(x) = \frac{3}{4} (x^2 - 1)^{2/3} \) using a graphing tool or calculator, starting from \( x = 1 \) as the function is not defined at \( x = \frac{1}{2} \). Observe where the function appears to reach any maximum or minimum values in the given interval \( [1, \, \infty) \).
03
Analyze the Graph
Upon plotting, observe that the function appears to increase from \( x = 1 \) onwards. It does not have a maximum value in the interval since it continues to rise indefinitely.
04
Use the TABLE Feature
Use the TABLE feature on a calculator to evaluate \( f(x) \) at specific points starting from \( x = 1 \). Check values such as \( x = 2, 3, 4 \), and note how \( f(x) \) increases. This confirms there's no maximum in this interval, and the minimum occurs at \( x = 1 \), which corresponds to the value of \( 0 \).
05
Confirm the Extreme Values
The absolute minimum in the interval \([1, \infty)\) is at \( x = 1 \) with \( f(1) = 0 \). There is no absolute maximum because \( f(x) \) increases indefinitely.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Absolute Extrema
Absolute extrema refer to the highest or lowest points that a function reaches over a particular interval. They are the points at which a function takes its largest or smallest values, called the absolute maximum or minimum, respectively.
To find absolute extrema, follow these steps:
To find absolute extrema, follow these steps:
- Identify critical points where the derivative of the function is zero or undefined.
- Evaluate the function at these critical points and at the endpoints of the interval.
- Compare these values to determine the highest and lowest values.
Power Function
A power function is a type of function that can be expressed in the form \( f(x) = ax^n \), where \( a \) is a constant, and \( n \) is a real number. In this exercise, the function \( f(x) = \frac{3}{4} (x^2 - 1)^{2/3} \) is a power function with a fractional exponent.
Understanding fractional exponents is crucial here:
Understanding fractional exponents is crucial here:
- Fractional exponents like \( (x^2 - 1)^{2/3} \) indicate a combination of root and power operations.
- The numerator of the fraction (\( 2 \)) represents the power, while the denominator (\( 3 \)) represents the root.
- This means \( (x^2 - 1)^{2/3} \) is equivalent to \( \sqrt[3]{(x^2 - 1)^2} \).
Graphical Analysis
Graphical analysis involves studying a function's graph to visually estimate important characteristics like trends, intercepts, and extrema. It complements numerical and algebraic analysis to give a comprehensive understanding of the function's behavior.
Here is how you can perform graphical analysis:
Here is how you can perform graphical analysis:
- Plot the function graph using a graphing tool, focusing on the defined domain.
- Look for areas where the function appears to level off or change direction, indicating potential extrema.
- Use tools like the TABLE feature of calculators to check values at strategic points.