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In Exercises 13-24, show that \(f\) and \(g\) are inverse functions (a) algebraically and (b) graphically. $$ f(x)=1-x^{3}, \quad g(x)=\sqrt[3]{1-x} $$

Short Answer

Expert verified
Yes, \(f(x)\) and \(g(x)\) are inverse functions to each other. This is shown algebraically since both \(f(g(x))\) and \(g(f(x))\) simplify to \(x\). The graphical proof requires graphing and visual inspection, but should confirm the result as well.

Step by step solution

01

Algebraic Proof

Firstly, the algebraic proof involves substituting \(g(x)\) into \(f(x)\) and vice versa, then simplifying to see if it results in \(x\). This will give us \(f(g(x))\) and \(g(f(x))\). Start by substituting \(g(x)\) into \(f(x)\): \[ f(g(x))=f(\sqrt[3]{1-x})=1-(\sqrt[3]{1-x})^{3}\]. Simplify this expression to see if it returns the original \(x\). Similarly, substitute \(f(x)\) into \(g(x)\): \[ g(f(x))=g(1-x^{3})=\sqrt[3]{1-(1-x^{3})}\]. Simplify this expression to see if it yields the original \(x\).
02

Simplification

After substitution, simplify both expressions. Simplification of \(f(g(x))\) gives: \[1-(\sqrt[3]{1-x})^{3}=1-(1-x)=x\]. This gives the original \(x\), as it was desired to proof. Doing the same for \(g(f(x))\), simplification gives: \[\sqrt[3]{1-(1-x^{3})}=\sqrt[3]{x^{3}}=x\]. This also gives back the original \(x\), proving that \(f(x)\) and \(g(x)\) are inverses algebraically.
03

Graphical Proof

To provide the graphical proof, it's needed to graph \(f(x)\), \(g(x)\), and the line \(y=x\) on the same graph. If \(f\) and \(g\) are indeed inverse functions, they will mirror each other across the line \(y=x\). This requires knowledge of graphing techniques for this type of functions, and likely the use of graphical software.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Algebraic Proof
Proving that two functions are inverses algebraically involves using function composition, which means that we need to substitute one function into the other. If they are indeed inverses, these compositions should simplify down to the variable they initially accepted, which is typically denoted as \(x\).

In this exercise, we start by checking if \(f(g(x)) = x\). By substituting \(g(x) = \sqrt[3]{1-x}\) into \(f(x) = 1-x^{3}\), we have:
  • \(f(g(x)) = 1 - (\sqrt[3]{1-x})^{3}\)
  • Simplification will show: \(1 - (1-x) = x\)
This checks out as it reduces to \(x\).

Next, we verify whether \(g(f(x)) = x\). By substituting \(f(x) = 1-x^{3}\) into \(g(x)\), we proceed in a similar fashion:
  • \(g(f(x)) = \sqrt[3]{1-(1-x^{3})}\)
  • Simplification will show: \(\sqrt[3]{x^{3}} = x\)
Both compositions simplify back to \(x\), confirming the inverse relationship between \(f\) and \(g\) algebraically.
Graphical Proof
Algebraic proof establishes a strong foundation, but graphical proof provides an intuitive visual confirmation. When evaluating if two functions, \(f\) and \(g\), are inverses, graphing them can reveal a symmetric relationship across the line \(y = x\).

To perform graphical proof:
  • Firstly, plot the graphs of \(f(x) = 1-x^{3}\), \(g(x) = \sqrt[3]{1-x}\), and the line \(y = x\).
  • When the graphs of \(f(x)\) and \(g(x)\) are mirror images over the line \(y = x\), it indicates they are inverse functions.
From the graph, you should see that the curve of \(f\) interrupts \(g\) exactly at points reflected over \(y = x\). This visual correspondence reinforces the algebraic conclusion that they are indeed inverses.
Function Composition
Understanding function composition is crucial when examining inverse functions. It involves calculating compositions like \(f(g(x))\) and \(g(f(x))\) to see if they revert to the identity function, represented as \(x\).

Discussing function composition:
  • Start with \(f(g(x))\); if it simplifies directly to \(x\), this serves as a strong indicator of inverse functions.
  • Perform \(g(f(x))\) as well. Simplifying this to \(x\) further reinforces the inverse relationship.
Function composition not only confirms inverses but also deepens the understanding of how these operations intertwine. When every composition operation untangles to \(x\), it spells out that both functions are perfect reflections of each other's operations, basis of their inverse nature. Understanding these concepts is key for deeper insight into algebraic structures and transformations.

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Most popular questions from this chapter

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