Chapter 1: Problem 52
(a) Graph \(y=x^{5 / 2}, x \geq 0\), and \(y=x^{1 / 2}, x \geq 0\), together, in
one coordinate system.
(b) Show algebraically that
$$
x^{5 / 2} \leq x^{1 / 2}
$$
for \(0 \leq x \leq 1\). (Hint: Show that \(x^{1 / 2} / x^{-1 / 2}=x \leq 1\) for
\(0
Short Answer
Expert verified
(a) Graph shows where one function is above another. (b) For \(0 < x \leq 1\), \(x^{5/2} \leq x^{1/2}\). (c) For \(x \geq 1\), \(x^{5/2} \geq x^{1/2}\).
Step by step solution
01
Graph Aquistion
To graph the functions \( y = x^{5/2} \) and \( y = x^{1/2} \) on the same coordinate system for \( x \geq 0 \), we need to observe the basic shapes of these functions. The function \( y = x^{1/2} \) is a square root function, which is concave downward and passes through the points like \( (0,0), (1,1), (4,2) \). The function \( y = x^{5/2} \) grows faster than \( y = x^{1/2} \) for \( x > 1 \) because it increases at a faster rate due to the higher exponent, but initially, for \( 0 < x < 1 \), it is less than or equal to \( y = x^{1/2} \). Plot the line \( y=x \) to observe the intersection points.
02
Analyzing Inequality for 0≤x≤1
Starting with the hint, we'll show \( \frac{x^{1/2}}{x^{-1/2}} = x \). Simplifying the fraction gives \( x^{1/2} \times x^{1/2} = x \), which equals \( x \). Since \( 0 \leq x \leq 1 \) clearly indicates that \( x \leq 1 \), this implies that for \( 0 < x \leq 1 \):\[x^{5/2} = (x^{1/2})^5 = (x^{1/2})(x^{1/2})^2(x^{1/2}) \]is less than or equal to \( x^{1/2} \) because \( x^{1/2} \times x \leq x^{1/2} \times 1 \). This means \( x^{5/2} \leq x^{1/2} \) when \( 0<x\leq1 \).
03
Analyzing Inequality for x≥1
For \( x \geq 1 \), we note that raising \( x \) to a higher power increases its value, i.e., \( x^{5/2} \geq x^{1/2} \). Writing \( x^{5/2} \) as \( (x^{1/2})^5 \), we can see:\[x^{5/2} = x^{1/2} imes x^2 \]As \( x \geq 1 \), then \( x^2 \geq x \geq 1 \), therefore \( x^{5/2} \geq x \geq x^{1/2} \). Hence, when \( x \geq 1 \), \( x^{5/2} \geq x^{1/2} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Inequalities
An inequality is a mathematical statement that shows the relationship of one quantity being greater or less than another. For expressions like those in our exercise,
- "\( x^{5/2} \leq x^{1/2} \) for \( 0 \leq x \leq 1 \)" means that for all values of \( x \) within the range from 0 to 1, the value of \( x^{5/2} \) is either less than or equal to \( x^{1/2} \).
- Conversely, "\( x^{5/2} \geq x^{1/2} \) for \( x \geq 1 \)" indicates that starting from \( x = 1 \), \( x^{5/2} \) will always be greater than or equal to \( x^{1/2} \).
Exponents
Exponents are a shorthand for repeated multiplication. If you see \( x^{n} \), it means that \( x \) is multiplied by itself \( n \) times. In our exercise:- The exponent \( \frac{5}{2} \) implies taking the squareroot followed by raising the result to the power of 5.- The expression \( x^{1/2} \) represents the square root of \( x \).**Properties of Exponents**
- Combining exponents, such as when multiplying like bases, involves adding their exponents: \( x^{a} \times x^{b} = x^{a+b} \).
- Power of a power involves multiplying: \( (x^{a})^{b} = x^{a\cdot b} \).
Functions
A function is essentially a rule that assigns each input exactly one output. In this exercise, we are dealing with functions \( y = x^{5/2} \) and \( y = x^{1/2} \). Understanding these helps to:- Predict the output of a range of inputs.- Analyze their algebraic properties like monotonicity or concavity.**Key Properties**- **Domain and Range**: For \( y = x^{5/2} \) and \( y = x^{1/2} \), both are defined where \( x \geq 0 \). The range for \( x \geq 0 \) for both functions is non-negative real numbers.- **Concavity**: \( y = x^{1/2} \) is concave down while \( y = x^{5/2} \) turns upward more steeply for larger \( x \), showing different growth behaviors.
- Concave down indicates that the slope is decreasing as \( x \) increases.
- For \( y = x^{5/2} \), larger exponents make the function grow faster over larger \( x \).
Graphing
Graphing is a visual method to understand functions and their relationships. By graphing the functions \( y = x^{5/2} \) and \( y = x^{1/2} \) on the same coordinate system, we can observe their interactions and compare their growth visually.**Graphing Benefits**
- Provides a clear, intuitive understanding of how functions increase or decrease over their domain.
- Identifies key points of intersection where the functions are equal - particularly useful in exercises that involve inequalities.