Chapter 1: Problem 52
In Exercises \(51-60\), show that \(f(g(x))=x\) and \(g(f(x))=x\). $$f(x)=\frac{x-2}{3}, \quad g(x)=3 x+2$$
Short Answer
Expert verified
\(f(g(x)) = x\) and \(g(f(x)) = x\), showing \(f\) and \(g\) are inverses.
Step by step solution
01
Compute \( f(g(x)) \)
First, substitute \( g(x) \) into the function \( f \). This means replacing \( x \) in \( f(x) = \frac{x-2}{3} \) with \( g(x) = 3x + 2 \). So:\[f(g(x)) = f(3x+2) = \frac{(3x+2) - 2}{3}\]Simplify the expression inside the fraction:\[f(g(x)) = \frac{3x}{3} = x\]
02
Compute \( g(f(x)) \)
Next, substitute \( f(x) \) into the function \( g \). This requires replacing \( x \) in \( g(x) = 3x + 2 \) with \( f(x) = \frac{x-2}{3} \). So:\[g(f(x)) = g\left(\frac{x-2}{3}\right) = 3\left(\frac{x-2}{3}\right) + 2\]Cancel out the \( 3 \) in the multiplication:\[g(f(x)) = (x-2) + 2 = x\]
03
Conclusion: Verify Inverses
The computations show that both \( f(g(x)) = x \) and \( g(f(x)) = x \). Therefore, \( f(x) \) and \( g(x) \) are inverse functions of each other.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Composition
Function composition is a fundamental concept in mathematics that allows you to combine functions into a single entity. Imagine you have two functions, \(f(x)\) and \(g(x)\), and you're curious about what happens when you apply both functions in succession.
Here's the step-by-step to understand function composition:
Here's the step-by-step to understand function composition:
- Start with the inner function: In the exercise, this was \(g(x)\).
- Substitute the result of the inner function into the outer function: Here, we substituted \(g(x)\) into \(f(x)\). This gave us \(f(g(x))\).
Algebraic Manipulation
Algebraic manipulation is the art of rearranging and simplifying expressions to make sense of them more easily. It involves a set of operations such as addition, subtraction, multiplication, division, and simplification.
In working with composite functions:
In working with composite functions:
- Simplify expressions: Once \(g(x) = 3x + 2\) was inserted into \(f(x) = \frac{x-2}{3}\), reducing \((3x + 2) - 2\) resulted directly in \(3x\). This was simplified further to \(x\) by dividing by 3.
- Handle fractions carefully: Inverses often involve fractions, like replacing \(x\) in \(g(x) = 3x + 2\) with the fraction \(f(x) = \frac{x-2}{3}\).
Function Notation
Function notation is a way of representing functions that clarifies which variable is being worked on at any point within an equation. It's like a placeholder that's waiting for a value to operate on.
Here are some insights into function notation:
Here are some insights into function notation:
- The function \(f(x)\) denotes the function \(f\) with \(x\) being the variable in question. Similarly, \(g(x)\) uses \(g\) for its operations on \(x\).
- When composing functions as \(f(g(x))\), it means \(g(x)\)'s result replaces any \(x\) in \(f(x)\). This marks a clear path of applying results from one function as inputs to another.