Chapter 3: Problem 53
Find the inverse function of \(f\) $$ f(x)=4-x^{2}, \quad x \geq 0 $$
Short Answer
Expert verified
The inverse function is \( f^{-1}(x) = \sqrt{4 - x} \), with domain \( 0 \leq x \leq 4 \).
Step by step solution
01
Define the function and replace
First, we identify the original function: \( f(x) = 4 - x^2 \) with the condition \( x \geq 0 \). To find the inverse, we start by replacing \( f(x) \) with \( y \). Thus, we have the equation \( y = 4 - x^2 \).
02
Swap variables
To find the inverse function, swap \( x \) and \( y \) in the equation from Step 1. This gives us \( x = 4 - y^2 \). The next step is to solve this equation for \( y \).
03
Solve for y
Rearrange the equation from Step 2 to isolate \( y^2 \). This gives us \( y^2 = 4 - x \). Next, take the square root of both sides to solve for \( y \). Since \( x \geq 0 \), we take the non-negative root: \( y = \sqrt{4 - x} \).
04
Define the inverse function
The function \( f^{-1}(x) \) is defined by \( y \). Therefore, the inverse function of \( f \) is \( f^{-1}(x) = \sqrt{4 - x} \). Note that the domain of this inverse function is \( 0 \leq x \leq 4 \), due to the condition \( x \geq 0 \) in the original function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Functions
Quadratic functions are polynomial functions of degree 2. The general form of a quadratic function is given by \( f(x) = ax^2 + bx + c \), where \( a \), \( b \), and \( c \) are constants and \( a eq 0 \). These functions graph into a shape called a parabola.
- The term \( ax^2 \) is the quadratic term, and it's the most crucial part because it determines the shape and direction of the parabola. If \( a > 0 \), the parabola opens upwards, and if \( a < 0 \), it opens downwards.
- In the exercise, the function \( f(x) = 4 - x^2 \) is a form of a downward opening parabola, indicating it is a quadratic function.
Domain and Range
The domain of a function is the set of all possible input values (\( x \)-values) that allow the function to work without errors. The range is the set of all possible output values (\( y \)-values).
- For a quadratic function like \( f(x) = 4 - x^2 \), the domain can sometimes have restrictions. In this case, \( x \geq 0 \) to satisfy the given problem requirements. This ensures that we only consider non-negative values for \( x \).
- The range for this specific function can be determined by finding the highest and lowest points on the parabola. Since it opens downward and is centered at \( y = 4 \), the range is \( (0, 4] \).
Solving Equations
Solving equations is an essential skill used to isolate a variable or find its value in terms of other variables. It involves rearranging expressions to get the desired variable alone on one side of the equation.
- When solving for the inverse of a function, like in the exercise \( f(x) = 4 - x^2 \), we first replaced \( f(x) \) with \( y \), obtaining \( y = 4 - x^2 \).
- To isolate \( y \), we swapped \( x \) and \( y \) to form \( x = 4 - y^2 \). The task then was to solve for \( y \).
- Upon rearranging, we had \( y^2 = 4 - x \). This required taking the square root of both sides, which rendered \( y = \sqrt{4 - x} \). Importantly, we only took the non-negative root due to the domain limitation \( x \geq 0 \), ensuring that the values reflect the original function's non-negative nature.