Math Problem Statement

Find the inverse of the function f(x) = x^3 - 5, check the answer, and determine the domain and range of both f(x) and its inverse.

Solution

Let's solve the problem step by step. The function provided is f(x)=x35f(x) = x^3 - 5, which is one-to-one. Here's how we can proceed:


(a) Find the inverse of f(x)f(x) and check the answer.

To find the inverse, follow these steps:

  1. Replace f(x)f(x) with yy: y=x35y = x^3 - 5

  2. Swap xx and yy to find the inverse: x=y35x = y^3 - 5

  3. Solve for yy: y3=x+5y^3 = x + 5 y=x+53y = \sqrt[3]{x + 5}

Thus, the inverse function is: f1(x)=x+53f^{-1}(x) = \sqrt[3]{x + 5}

Check: To verify, substitute f(f1(x))f(f^{-1}(x)) and f1(f(x))f^{-1}(f(x)) to confirm they return xx:

  • f(f1(x))=(x+53)35=x+55=xf(f^{-1}(x)) = (\sqrt[3]{x + 5})^3 - 5 = x + 5 - 5 = x,
  • f1(f(x))=(x35)+53=x33=xf^{-1}(f(x)) = \sqrt[3]{(x^3 - 5) + 5} = \sqrt[3]{x^3} = x.

The inverse is correct.


(b) Find the domain and range of ff and f1f^{-1}.

  1. Domain of f(x)=x35f(x) = x^3 - 5:

    • Since x35x^3 - 5 is defined for all real xx, the domain is: (,)(-\infty, \infty)
  2. Range of f(x)=x35f(x) = x^3 - 5:

    • The cubic function x3x^3 spans all real values, and subtracting 5 does not limit the output. Thus, the range is: (,)(-\infty, \infty)
  3. Domain of f1(x)=x+53f^{-1}(x) = \sqrt[3]{x + 5}:

    • The cube root is defined for all real x+5x + 5. Thus, the domain is: (,)(-\infty, \infty)
  4. Range of f1(x)=x+53f^{-1}(x) = \sqrt[3]{x + 5}:

    • The cube root also spans all real numbers, so the range is: (,)(-\infty, \infty)

(c) Graph f(x)f(x), f1(x)f^{-1}(x), and y=xy = x on the same coordinate axes.

You would graph:

  • f(x)=x35f(x) = x^3 - 5, a cubic function shifted down by 5 units.
  • f1(x)=x+53f^{-1}(x) = \sqrt[3]{x + 5}, the reflection of f(x)f(x) across y=xy = x.
  • y=xy = x, a straight diagonal line passing through the origin.

Answering the multiple-choice questions:

  1. Range of f(x)f(x): The range of f(x)f(x) is all real numbers:

    • Correct answer: D. The range is the set of all real numbers.\text{D. The range is the set of all real numbers.}
  2. Domain of f1(x)f^{-1}(x): The domain of f1(x)f^{-1}(x) is all real numbers:

    • Correct answer: D. The domain is the set of all real numbers.\text{D. The domain is the set of all real numbers.}

Do you want me to graph the functions or explain any specific step further?

Questions to Explore:

  1. How do we determine if a function is one-to-one?
  2. What is the process of finding the inverse of non-linear functions?
  3. Can the domain or range ever be restricted for cubic functions?
  4. How does the graph of f(x)f(x) relate to its inverse f1(x)f^{-1}(x)?
  5. What happens to the graph when constants are added or subtracted to cubic functions?

Tip:

When finding inverses, always check your result by substituting into the original function to ensure they undo each other.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Inverse Functions
Cubic Functions
Domain and Range

Formulas

f^{-1}(x) = \sqrt[3]{x + 5}
f(x) = x^3 - 5

Theorems

One-to-One Function Theorem
Inverse Function Theorem

Suitable Grade Level

Grades 10-12