Math Problem Statement

Identify the range and domain for the inverse of the following function: f(x)=8-(x+5)^2

Solution

To find the range and domain for the inverse of the function f(x)=8(x+5)2f(x) = 8 - (x + 5)^2, we need to follow a few steps.

Step 1: Determine the domain and range of f(x)f(x)

The given function f(x)=8(x+5)2f(x) = 8 - (x + 5)^2 is a downward-opening parabola. To find the domain and range of f(x)f(x):

  1. Domain of f(x)f(x):
    The function f(x)=8(x+5)2f(x) = 8 - (x + 5)^2 is defined for all real numbers xx. Therefore, the domain is: Domain of f(x)=(,)\text{Domain of } f(x) = (-\infty, \infty)

  2. Range of f(x)f(x):
    The vertex of the parabola y=8(x+5)2y = 8 - (x + 5)^2 occurs at x=5x = -5. At this point, y=8y = 8. Since the parabola opens downwards, the maximum value is 88 and it decreases without bound as xx moves away from 5-5. Therefore, the range is: Range of f(x)=(,8]\text{Range of } f(x) = (-\infty, 8]

Step 2: Find the inverse of f(x)f(x)

To find the inverse, we first set y=f(x)y = f(x):

y=8(x+5)2y = 8 - (x + 5)^2

Solving for xx:

y8=(x+5)2y - 8 = -(x + 5)^2

(y8)=(x+5)2-(y - 8) = (x + 5)^2

x+5=±8yx + 5 = \pm \sqrt{8 - y}

x=5±8yx = -5 \pm \sqrt{8 - y}

Since f(x)f(x) is a function, its inverse must also be a function. To ensure f1(x)f^{-1}(x) is a function, we restrict the domain of f(x)f(x) to where it is one-to-one. Considering x5x \geq -5:

x=5+8yx = -5 + \sqrt{8 - y}

Thus, the inverse function f1(y)f^{-1}(y) is:

f1(y)=5+8yf^{-1}(y) = -5 + \sqrt{8 - y}

Step 3: Determine the domain and range of f1(y)f^{-1}(y)

  1. Domain of f1(y)f^{-1}(y):
    The range of f(x)f(x) becomes the domain of f1(y)f^{-1}(y). Therefore, the domain is: Domain of f1(y)=(,8]\text{Domain of } f^{-1}(y) = (-\infty, 8]

  2. Range of f1(y)f^{-1}(y):
    The domain of f(x)f(x) becomes the range of f1(y)f^{-1}(y). Therefore, the range is: Range of f1(y)=[5,)\text{Range of } f^{-1}(y) = [-5, \infty)

Summary

  • The domain of the inverse function f1(y)f^{-1}(y) is (,8](-\infty, 8].
  • The range of the inverse function f1(y)f^{-1}(y) is [5,)[-5, \infty).

Would you like more details or have any questions?

Here are some questions you might want to explore next:

  1. How do you find the inverse of a different function?
  2. What are the properties of inverse functions?
  3. How do you verify that two functions are inverses of each other?
  4. What are the transformations of the graph of f(x)f(x)?
  5. How do the concepts of domain and range apply to real-world problems?

Tip: When finding the inverse of a function, always ensure that the original function is one-to-one on its domain, otherwise restrict the domain to make it one-to-one.

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Math Problem Analysis

Mathematical Concepts

Functions
Inverse Functions
Quadratic Functions

Formulas

Quadratic function: f(x) = a(x - h)^2 + k
Inverse function formula

Theorems

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Suitable Grade Level

Grades 11-12