Math Problem Statement

Determine the equation of the inverse of f(x) = x^2 - 4x + 24.

Solution

For Question 17, the function given is:

f(x)=x24x+24f(x) = x^2 - 4x + 24

To find the inverse of this function, let's follow these steps:

Step 1: Set y=f(x)y = f(x)

y=x24x+24y = x^2 - 4x + 24

Step 2: Solve for xx in terms of yy

First, complete the square to rewrite the quadratic expression: y=(x24x)+24y = (x^2 - 4x) + 24

To complete the square, take half of the coefficient of xx (which is -4), square it, and add/subtract it inside the equation: y=(x24x+44)+24=(x2)2+20y = (x^2 - 4x + 4 - 4) + 24 = (x - 2)^2 + 20

Now the equation is: y=(x2)2+20y = (x - 2)^2 + 20

Step 3: Isolate the square term

y20=(x2)2y - 20 = (x - 2)^2

Step 4: Take the square root of both sides

y20=x2\sqrt{y - 20} = x - 2

Step 5: Solve for xx

x=2±y20x = 2 \pm \sqrt{y - 20}

Step 6: Swap xx and yy to express the inverse function

y=2±x20y = 2 \pm \sqrt{x - 20}

Thus, the inverse function is: y=2±x20y = 2 \pm \sqrt{x - 20}

Conclusion:

Looking at the answer choices, the correct one is:

y=2±x20y = 2 \pm \sqrt{x - 20}

This matches the first option.


Would you like further details or clarifications?

Related questions:

  1. How do you complete the square for quadratic expressions?
  2. What is the method to find the inverse of a function algebraically?
  3. Can the inverse of any function be found, and if not, why?
  4. How does completing the square help in solving quadratic equations?
  5. What is the significance of the square root in the inverse function?

Tip:

Always verify if the original function is one-to-one before solving for the inverse.

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Math Problem Analysis

Mathematical Concepts

Inverse functions
Quadratic equations
Completing the square

Formulas

y = f(x)
Completing the square
Inverse of a function

Theorems

The process of finding the inverse of a quadratic function

Suitable Grade Level

High School