Chapter 0: Problem 19
Find a formula for \(f^{-1}(x)\), and state the domain of the function \(f^{-1}\). \(f(x)=-\sqrt{3-2 x}\)
Short Answer
Expert verified
The inverse function is \(f^{-1}(x) = \frac{3-x^2}{2}\) with domain \(-\sqrt{3} \leq x \leq 0\).
Step by step solution
01
Understand the function and its domain
The function given is \( f(x) = -\sqrt{3-2x} \). It's important to note that the square root function is only defined for non-negative numbers, i.e., the expression inside must be greater than or equal to 0. Therefore, \( 3 - 2x \geq 0 \). Solving this inequality, we have \( 2x \leq 3 \) or \( x \leq \frac{3}{2} \). This represents the domain of \( f(x) \).
02
Set up the equation for the inverse
To find the inverse, we start by setting \( y = f(x) = -\sqrt{3-2x} \). The goal is to express \( x \) in terms of \( y \).
03
Isolate the square root
Multiply both sides by \(-1\) to positive the square root expression. This gives us \( -y = \sqrt{3-2x} \).
04
Square both sides
Square both sides to eliminate the square root: \((-y)^2 = (\sqrt{3-2x})^2\). This yields \(y^2 = 3-2x\).
05
Solve for \(x\)
Rearrange the equation obtained from squaring both sides to solve for \(x\): \(2x = 3 - y^2\). Hence, \(x = \frac{3-y^2}{2}\). This expression is \( f^{-1}(y) \).
06
Determine the domain of \(f^{-1}\)
The domain of \(f^{-1}\) corresponds to the range of \( f(x) = -\sqrt{3-2x} \). Since a square root function results in non-negative outputs, \(-\sqrt{3-2x}\) must be less than or equal to 0. Thus, the range is \(- \sqrt{3} \leq y \leq 0\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Domain of a Function
The domain of a function refers to all the possible input values (or "x" values) that a function can accept without causing any mathematical problems, such as division by zero or taking the square root of a negative number. For the function \( f(x) = -\sqrt{3 - 2x} \), we face a square root, which is only defined for non-negative numbers. This means the expression under the square root, \(3 - 2x\), must be greater than or equal to zero.
To find the domain, set up the inequality:
To find the domain, set up the inequality:
- \(3 - 2x \geq 0\).
- Solve for \(x\) to find \(2x \leq 3\) or \(x \leq \frac{3}{2}\).
Square Roots
Square roots are a common component in mathematics, symbolized by the radical \(\sqrt{}\). The square root of a number \(a\) is a number \(x\) such that \(x^2 = a\). Importantly, square roots only produce non-negative results when working with real numbers. This is why our function \( f(x) = -\sqrt{3 - 2x} \) was constrained by the inequality \(3 - 2x \geq 0\).
Here’s what you need to remember about square roots:
Here’s what you need to remember about square roots:
- The expression inside the square root (called the radicand) must be non-negative in real number solutions.
- Squaring the square root cancels it out, allowing you to solve for unknowns if you isolate it appropriately.
Inequalities
Inequalities describe a relationship where one quantity is bigger or smaller than another. They are often depicted with signs such as \(>\), \(<\), \(\geq\), and \(\leq\). In our function \( f(x) = -\sqrt{3-2x} \), an inequality shows up when determining the domain. Calculating \(3 - 2x \geq 0\) tells us for which values of \(x\) the function is defined.
Handling inequalities involves a few key steps:
Handling inequalities involves a few key steps:
- Solve similarly to equations: isolate the variable on one side by performing valid operations on both sides.
- Careful with multiplication or division: If you multiply or divide both sides by a negative number, flip the inequality sign.
- Graphing: Visualize inequalities on a number line to better understand the solution set.
Range of a Function
The range of a function includes all the possible output values (or "y" values) which come from the function's input domain. It's essentially the set of all possible end results a function can produce with its defined inputs. For \(f(x) = -\sqrt{3 - 2x}\), the outputs must be non-positive since the square root itself is non-negative, but it is multiplied by \(-1\).
To determine the range of \( f \), consider:
To determine the range of \( f \), consider:
- The smallest possible value for \(y\): When the expression inside the square root is its maximum (at \(x = -\infty\)), \(y\) approaches 0.
- The largest possible value for \(y\): When \(x = \frac{3}{2}\), the expression inside is 0, making \(y = -\sqrt{0} = 0\).