Math Problem Statement

Find the inverse of the function f(x) given, then prove (by composition) your inverse function is correct. Note the domain of f is all real numbers. f(x) = ∛(3x - 2)

Solution

The function provided is:

f(x)=3x23f(x) = \sqrt[3]{3x - 2}

Step 1: Find the inverse function

To find the inverse of a function f(x)f(x), follow these steps:

  1. Replace f(x)f(x) with yy: y=3x23y = \sqrt[3]{3x - 2}

  2. Swap xx and yy (this reflects finding the inverse): x=3y23x = \sqrt[3]{3y - 2}

  3. Now, solve for yy:

    • Cube both sides to remove the cube root: x3=3y2x^3 = 3y - 2
    • Isolate yy: 3y=x3+23y = x^3 + 2 y=x3+23y = \frac{x^3 + 2}{3}

So, the inverse function is:

f1(x)=x3+23f^{-1}(x) = \frac{x^3 + 2}{3}

Step 2: Prove the inverse by composition

To verify that f1(x)f^{-1}(x) is the correct inverse, we need to check two conditions:

  1. f(f1(x))=xf(f^{-1}(x)) = x
  2. f1(f(x))=xf^{-1}(f(x)) = x

1. Prove f(f1(x))=xf(f^{-1}(x)) = x:

Substitute f1(x)=x3+23f^{-1}(x) = \frac{x^3 + 2}{3} into f(x)=3x23f(x) = \sqrt[3]{3x - 2}: f(f1(x))=f(x3+23)=3(x3+23)23f(f^{-1}(x)) = f\left( \frac{x^3 + 2}{3} \right) = \sqrt[3]{3 \left( \frac{x^3 + 2}{3} \right) - 2} Simplify the expression inside the cube root: [ f(f^{-1}(x)) = \sqrt[3]{x^3 + 2 - 2} = \sqrt[3]{x^3} = x ] This shows that f(f1(x))=xf(f^{-1}(x)) = x.

2. Prove f1(f(x))=xf^{-1}(f(x)) = x:

Substitute f(x)=3x23f(x) = \sqrt[3]{3x - 2} into f1(x)=x3+23f^{-1}(x) = \frac{x^3 + 2}{3}: [ f^{-1}(f(x)) = f^{-1}\left( \sqrt[3]{3x - 2} \right) = \frac{\left( \sqrt[3]{3x - 2} \right)^3 + 2}{3} ] Simplify the expression: f1(f(x))=3x2+23=3x3=xf^{-1}(f(x)) = \frac{3x - 2 + 2}{3} = \frac{3x}{3} = x This shows that f1(f(x))=xf^{-1}(f(x)) = x.

Conclusion:

Since both compositions result in xx, we have verified that the inverse function is correct:

f1(x)=x3+23f^{-1}(x) = \frac{x^3 + 2}{3}

Let me know if you would like further clarifications or details. Here are some related questions:

  1. How do you find the inverse of more complex functions?
  2. What is the domain and range of the inverse function?
  3. Can you explain why the domain of f(x)f(x) is all real numbers?
  4. How does composition help in verifying inverse functions?
  5. What other methods exist for verifying inverse functions?

Tip: When solving for the inverse of a function, always check if the function is one-to-one, as this ensures that it has an inverse.

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Math Problem Analysis

Mathematical Concepts

Inverse Functions
Function Composition
Domain and Range
Cubic Roots

Formulas

Inverse of a function formula
Cubic root formula
Function composition: f(f^(-1)(x)) = x and f^(-1)(f(x)) = x

Theorems

Theorem of inverse functions
Properties of cube roots and cubic equations

Suitable Grade Level

Grades 10-12 (High School Algebra and Precalculus)