Chapter 6: Problem 71
The given function \(f\) is one-to-one. Find \(f^{-1}(x)\). $$f(x)=\sqrt{x^{2}-4}, x \geq 2$$
Short Answer
Expert verified
The inverse function is \( f^{-1}(x) = \sqrt{x^2 + 4} \).
Step by step solution
01
Understand the Function Definition
The function given is \( f(x) = \sqrt{x^2 - 4} \) with \( x \geq 2 \). This function is defined for all values of \( x \) such that \( x^2 - 4 \geq 0 \), i.e., \( x \geq 2 \), meaning it is a one-to-one function as specified.
02
Express y in terms of x
To find the inverse, first express the function in terms of \( y \, = \, f(x) \):\[ y = \sqrt{x^2 - 4} \]
03
Square Both Sides
Eliminate the square root by squaring both sides:\[ y^2 = x^2 - 4 \]
04
Solve for x
Isolate \( x^2 \) by adding 4 to both sides:\[ x^2 = y^2 + 4 \]
05
Solve for x with the correct conditions
Since \(x \geq 2\), when taking the square root, we consider the positive root:\[ x = \sqrt{y^2 + 4} \]
06
Write the Inverse Function
Express \( x \) in terms of \( y \), considering it as the inverse function:\[ f^{-1}(x) = \sqrt{x^2 + 4} \] where \( x \geq 0 \) as derived from squaring.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
One-to-One Functions
A one-to-one function is a special type of function where each input corresponds to a unique output, and each output corresponds to a unique input. Understanding if a function is one-to-one is important because it helps us determine if an inverse function exists. A simple way to check if a function is one-to-one is by using the Horizontal Line Test.
- Draw a horizontal line across the graph of the function.
- If any horizontal line intersects the graph more than once, the function is not one-to-one.
- If no horizontal line intersects the graph more than once, the function is one-to-one.
Domain and Range
Understanding the domain and range of a function is essential in analyzing how the function behaves. The domain is the set of all possible input values (\( x \)) for the function, while the range is the set of all possible output values (\( y \)). For the function \( f(x) = \sqrt{x^2 - 4} \), determining the domain involves ensuring the expression inside the square root is non-negative.
- The function is defined when \( x^2 - 4 \geq 0 \), which simplifies to \( x \geq 2 \).
- Therefore, the domain of \( f(x) \) is \([2, \infty)\).
- Since the square root function produces non-negative outputs, the smallest value \( f(x) \) can be is 0 when \( x = 2 \).
- The range of \( f(x) \) thus becomes \([0, \infty)\).
Square Root Functions
Square root functions are functions that involve the square root of a variable or expression. In the function \( f(x) = \sqrt{x^2 - 4} \), the square root affects how the function behaves visually and mathematically.Square root functions typically:
- Start from a certain value and increase slowly because squaring grows quite fast.
- Always produce non-negative outputs by default.