Chapter 2: Problem 39
The given function \(f\) is one-to-one. Find \(f^{-1}\). Proceed as in part (b) of Example 4 and find the domain and range of \(f^{-1}\). Then find the range of \(f\). $$ f(x)=\frac{1}{2 x-1} $$
Short Answer
Expert verified
The inverse function is \(f^{-1}(x) = \frac{1 + x}{2x}\), with domain \(x \neq 0\) and range \(y \neq \frac{1}{2}\). The range of \(f\) is \(y \neq 0\).
Step by step solution
01
Express the Function with y
To find the inverse function, start by replacing \(f(x)\) with \(y\). So the equation becomes \(y = \frac{1}{2x - 1}\).
02
Swap x and y
Change \(y\) to \(x\) and solve for \(y\). After swapping, the equation will be \(x = \frac{1}{2y - 1}\).
03
Solve for y
To find \(y\), manipulate the equation \(x = \frac{1}{2y - 1}\):1. Multiply both sides by \(2y - 1\): \(x(2y - 1) = 1\).2. Distribute \(x\): \(2xy - x = 1\).3. Add \(x\) to both sides: \(2xy = 1 + x\).4. Solve for \(y\): \(y = \frac{1 + x}{2x}\).Thus, the inverse function is \(f^{-1}(x) = \frac{1 + x}{2x}\).
04
Determine the Domain of \(f^{-1}\)
The domain of \(f^{-1}(x)\) is all real numbers except where the denominator is zero.For \(f^{-1}(x) = \frac{1 + x}{2x}\), the denominator is zero when \(x = 0\). Thus, the domain of \(f^{-1}\) is \(x eq 0\).
05
Determine the Range of \(f^{-1}\)
The range of \(f^{-1}\) is the same as the domain of the original function, \(f(x)\). For \(f(x) = \frac{1}{2x - 1}\), the denominator cannot be zero, so \(2x - 1 eq 0\). Solving gives \(x eq \frac{1}{2}\). Thus, the range of \(f^{-1}\) is \(y eq \frac{1}{2}\).
06
Determine the Range of f
Finally, the range of \(f\) is the same as the domain of \(f^{-1}\), which is all real numbers except zero. Therefore, the range of \(f\) is \(y eq 0\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Domain and Range
When we talk about the **domain and range** of a function, it means we are discussing the input values the function can take (domain) and the output values it can produce (range). In this exercise, we are working with a rational function, which is a fraction where the numerator and denominator are both polynomials.
For the original function, \( f(x) = \frac{1}{2x - 1} \), let's discuss its domain:
For the original function, \( f(x) = \frac{1}{2x - 1} \), let's discuss its domain:
- The denominator \( 2x - 1 \) cannot be zero because division by zero is undefined.
- Solving for when the denominator is zero: \( 2x - 1 = 0 \) gives \( x = \frac{1}{2} \).
- Therefore, the domain of \( f(x) \) is all real numbers except \( x = \frac{1}{2} \).
- The range is the set of all possible \( y \) values that the function can output.
- In this function, \( f(x) \) will never touch or return zero because it implies the denominator of the inverse function becomes undefined.
- This means the range of \( f(x) \) is all real numbers except \( y = 0 \).
- The domain is all real numbers except zero, \( x eq 0 \), because zero makes the denominator undefined.
One-to-one Function
A **one-to-one function** is a special kind of function where each input (or \( x \)-value) is associated with exactly one output (or \( y \)-value), and vice versa. This is an essential property when finding inverse functions. If a function is not one-to-one, its inverse will not be a function unless the domain is restricted.
In the exercise problem, we have: \( f(x) = \frac{1}{2x - 1} \) is specified to be one-to-one. Here's how this works:
In the exercise problem, we have: \( f(x) = \frac{1}{2x - 1} \) is specified to be one-to-one. Here's how this works:
- This means for every unique \( x \, (x eq \frac{1}{2}) \), there will be a unique \( y \).
- Since no two different \( x \)-values can produce the same \( y \)-value, we can find an inverse.
- Imagine drawing horizontal lines across the graph of the function. If any line touches the graph more than once, the function is not one-to-one.
- For \( f(x) \), each horizontal line only touches in one place due to its nature as a rational function—making it one-to-one.
Rational Functions
**Rational functions** are those that can be expressed as the quotient of two polynomials. They have the general form \( f(x) = \frac{P(x)}{Q(x)} \), where both \( P(x) \) and \( Q(x) \) are polynomials.
They are characterized by the following:
They are characterized by the following:
- They can have both vertical asymptotes and horizontal asymptotes.
- The vertical asymptote occurs where the denominator is zero and the function is undefined.
- The horizontal asymptote describes the behavior of the function as \( x \) approaches infinity.
- A simple rational function with a single vertical asymptote at \( x = \frac{1}{2} \), where \( 2x - 1 = 0 \).
- There is no horizontal asymptote as \( x \) tends to infinity, because the degree of the numerator (0, constant 1) is less than the degree of the denominator (1).