Math Problem Statement

Find the inverse of the given​ one-to-one function f. Give the domain and the range of f and of

f Superscript negative 1f−1​,

and graph both f and

f Superscript negative 1f−1

on the same set of axes.

f left parenthesis x right parenthesis equals StartFraction x plus 2 Over x minus 5 EndFractionf(x)=x+2x−5

what is also the domain and range in interval notation

Solution

To find the inverse of the function f(x)=x+2x5f(x) = \frac{x + 2}{x - 5}, let’s go through the steps to find the inverse, determine the domain and range of both ff and f1f^{-1}, and then discuss how they would be graphed.

Step 1: Find the Inverse Function

  1. Rewrite f(x)f(x) as yy: y=x+2x5y = \frac{x + 2}{x - 5}

  2. Swap xx and yy to find f1(x)f^{-1}(x): x=y+2y5x = \frac{y + 2}{y - 5}

  3. Solve for yy: Multiply both sides by y5y - 5: x(y5)=y+2x(y - 5) = y + 2 Distribute xx: xy5x=y+2xy - 5x = y + 2 Move terms involving yy to one side: xyy=5x+2xy - y = 5x + 2 Factor out yy: y(x1)=5x+2y(x - 1) = 5x + 2 Divide by x1x - 1 to solve for yy: y=5x+2x1y = \frac{5x + 2}{x - 1}

So, the inverse function is: f1(x)=5x+2x1f^{-1}(x) = \frac{5x + 2}{x - 1}

Step 2: Determine the Domain and Range

For the function f(x)=x+2x5f(x) = \frac{x + 2}{x - 5}:

  • Domain of ff: The function f(x)f(x) is undefined when the denominator x5=0x - 5 = 0, which gives x=5x = 5. Thus, the domain of ff is all real numbers except x=5x = 5: Domain of f:(,5)(5,)\text{Domain of } f: (-\infty, 5) \cup (5, \infty)

  • Range of ff: The function f(x)f(x) approaches all real values as xx varies, but it cannot equal 1 (since f(x)=1f(x) = 1 would imply x=5x = 5, which is excluded from the domain). Therefore, the range of ff is all real numbers except 1: Range of f:(,1)(1,)\text{Range of } f: (-\infty, 1) \cup (1, \infty)

For the inverse function f1(x)=5x+2x1f^{-1}(x) = \frac{5x + 2}{x - 1}:

  • Domain of f1f^{-1}: Similar reasoning applies, where the inverse function is undefined for x=1x = 1. Thus, the domain of f1f^{-1} is: Domain of f1:(,1)(1,)\text{Domain of } f^{-1}: (-\infty, 1) \cup (1, \infty)

  • Range of f1f^{-1}: The range of f1f^{-1} will match the domain of ff, so it is: Range of f1:(,5)(5,)\text{Range of } f^{-1}: (-\infty, 5) \cup (5, \infty)

Step 3: Graphing ff and f1f^{-1}

To graph f(x)f(x) and f1(x)f^{-1}(x) on the same set of axes, you would plot both functions. They will be symmetric about the line y=xy = x, as this line reflects a function and its inverse.

Would you like to see a plot of these functions, or do you need further clarification on any step?


Here are 5 follow-up questions to deepen understanding:

  1. Why is the line y=xy = x the axis of symmetry for a function and its inverse?
  2. What would change if we shifted f(x)f(x) horizontally or vertically?
  3. How can we verify that f1(x)f^{-1}(x) we found is indeed the inverse of f(x)f(x)?
  4. How would the domain and range change if f(x)f(x) had an additional term, such as f(x)=x+2x5+3f(x) = \frac{x + 2}{x - 5} + 3?
  5. What types of real-world problems involve finding the inverse of a function?

Tip: Remember that a function and its inverse will "undo" each other, meaning f(f1(x))=xf(f^{-1}(x)) = x and f1(f(x))=xf^{-1}(f(x)) = x. This is a good way to check if you've found the correct inverse.

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Math Problem Analysis

Mathematical Concepts

Functions
Inverse Functions
Domain and Range
Algebra

Formulas

f(x) = (x + 2) / (x - 5)
f^{-1}(x) = (5x + 2) / (x - 1)

Theorems

Inverse of a function
Domain and range of rational functions

Suitable Grade Level

Grades 9-11