Problem 42 - Algebra 2

Question

Find the inverse of each function. Is the inverse a function? $$ f(x)=x^{4} $$

Step-by-Step Solution

Answer

The inverse of the function \(f(x)=x^{4}\) is \(y=\sqrt[4]{x}\) and \(y=-\sqrt[4]{x}\), which is not a function as it does not pass the vertical line test.

Step 1: Swap the \(x\) and \(y\)

Replace \(f(x)\) with \(y\), getting \(y=x^{4}\). After, swap \(x\) and \(y\) getting \(x=y^{4}\)

Step 2: Solve for \(y\)

To solve for \(y\), solve the equation \(x=y^{4}\). This results in \(y=\sqrt[4]{x}\) and \(y=-\sqrt[4]{x}\)

Step 3: Verify if the inverse is a function

The inverse \(y=\sqrt[4]{x}\) and \(y=-\sqrt[4]{x}\) do not pass the vertical line test, because for any given value of \(x\), there exist two corresponding values of \(y\). So the inverse is not a function itself.

Key Concepts

Function Analysis

When you are faced with finding the inverse of a function, the process starts with a detailed function analysis. Understanding the original function's behavior is crucial. For example, take the function \( f(x) = x^4 \). In this scenario, we need to analyze whether the function stretches, compresses, or has certain symmetrical properties before finding its inverse.
To conduct a thorough function analysis:

• Determine the function type: Here, \( f(x) = x^4 \) is a power function with even exponent.
• Check symmetry: This function is symmetric about the y-axis, making it even.
• Identify range and domain: Normally, the range of \( f(x) = x^4 \) is \([0, \, \, \infty )\), while its domain is \(( - \infty, \, \infty)\).

Understanding these properties assures that we account for potential difficulties when finding an inverse, such as ensuring the inverse relation must be defined correctly.

Vertical Line Test

The vertical line test is a simple method to check if a graph represents a function. If any vertical line drawn through the graph intersects the curve at more than one point, the graph does not represent a function.
This test is crucial in verifying that the inverse of \( f(x) \) is valid as a function. In the scenario where we derive the inverse \( y = \sqrt[4]{x} \) and \( y = -\sqrt[4]{x} \), applying the vertical line test reveals a failure - any value of \( x \) introduces two corresponding \( y \)-values. Consequently, the inverse fails as a function because a function by definition cannot assign multiple outputs to a single input.

Solving Equations

Solving equations is at the heart of finding an inverse. To get the inverse from \( f(x) = x^4 \), you newly define \( y = x^4 \) and then swap \( x \) and \( y \). This gives you \( x = y^4 \), an equation needing solving for \( y \).
At this point, you apply inverse operations. In this problem, you'd take the fourth root, symbolically written as \( y = \sqrt[4]{x} \). Remember, there are two possible roots: the positive and the negative, so you indeed get two solutions: \( y = \sqrt[4]{x} \) and \( y = -\sqrt[4]{x} \). These solutions indicate the potential inverse relationships, yet this duality means multiple outputs for single inputs, confusing the statement that the result should be a function.

Inverse Relation

An inverse relation reverses the roles of inputs and outputs from the original function. Initially, in our example \( f(x) = x^4 \), we switch \( x \) and \( y \), giving you the equation \( x = y^4 \). When tackling inverse relations, it is critically about finding if this turned-around relationship constitutes a valid function again by checking the domain and range after manipulation.
The calculation of inverse relation guarantees determining different pairs of related terms, but it doesn't necessarily guarantee function exclusivity. Thus, the end goal often extends to checking if the resulting expression can legitimately be termed an inverse function. In this case, due to gaining two values from a single \( x \)-input, \( y = \sqrt[4]{x} \) and \( y = -\sqrt[4]{x} \) together comprise an inverse relation but lack the precision to be defined solely as a function.