Math Problem Statement

find the following inverse functions. 1) f(x)=5x2 f\left(x\right)=5x-2\text{ }2)f(x)=12x+4f\left(x\right)=\frac12x+4 3)f(x)=2(x3)2+1f\left(x\right)=2\left(x-3\right)^2+1

Solution

Let’s find the inverses for the given functions step by step.


1. For f(x)=5x2f(x) = 5x - 2:

To find the inverse:

  1. Replace f(x)f(x) with yy:
    y=5x2y = 5x - 2.
  2. Swap xx and yy:
    x=5y2x = 5y - 2.
  3. Solve for yy:
    x+2=5y    y=x+25.x + 2 = 5y \implies y = \frac{x + 2}{5}.

Inverse function:
f1(x)=x+25.f^{-1}(x) = \frac{x + 2}{5}.


2. For f(x)=12x+4f(x) = \frac{1}{2}x + 4:

To find the inverse:

  1. Replace f(x)f(x) with yy:
    y=12x+4y = \frac{1}{2}x + 4.
  2. Swap xx and yy:
    x=12y+4x = \frac{1}{2}y + 4.
  3. Solve for yy:
    x4=12y    y=2(x4).x - 4 = \frac{1}{2}y \implies y = 2(x - 4).

Inverse function:
f1(x)=2(x4).f^{-1}(x) = 2(x - 4).


3. For f(x)=2(x3)2+1f(x) = 2(x - 3)^2 + 1:

To find the inverse:

  1. Replace f(x)f(x) with yy:
    y=2(x3)2+1y = 2(x - 3)^2 + 1.
  2. Swap xx and yy:
    x=2(y3)2+1x = 2(y - 3)^2 + 1.
  3. Solve for yy:
    x1=2(y3)2    x12=(y3)2.x - 1 = 2(y - 3)^2 \implies \frac{x - 1}{2} = (y - 3)^2. Taking the square root (± for both branches): y3=±x12    y=3±x12.y - 3 = \pm \sqrt{\frac{x - 1}{2}} \implies y = 3 \pm \sqrt{\frac{x - 1}{2}}.

Since the original function is not one-to-one, its inverse has two branches:
f1(x)=3+x12andf1(x)=3x12.f^{-1}(x) = 3 + \sqrt{\frac{x - 1}{2}} \quad \text{and} \quad f^{-1}(x) = 3 - \sqrt{\frac{x - 1}{2}}.


Summary of Inverses:

  1. f1(x)=x+25f^{-1}(x) = \frac{x + 2}{5}
  2. f1(x)=2(x4)f^{-1}(x) = 2(x - 4)
  3. f1(x)=3±x12f^{-1}(x) = 3 \pm \sqrt{\frac{x - 1}{2}}

Would you like further clarification or detailed steps for any of these?


Related Questions:

  1. How can we determine whether a function has an inverse before solving?
  2. What is the graphical interpretation of a function and its inverse?
  3. What happens if a function is not one-to-one? Can it still have an inverse?
  4. How can we verify that our calculated inverse is correct?
  5. Can a quadratic function ever have a single-valued inverse?

Tip: Always check if the original function is one-to-one by applying the horizontal line test before finding the inverse!

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Math Problem Analysis

Mathematical Concepts

Inverse functions
Algebraic manipulation
Quadratic equations

Formulas

Inverse formula: Swap x and y, then solve for y
Square root property: ±√(x)
General quadratic form: y = a(x - h)^2 + k

Theorems

Horizontal Line Test (to check one-to-one functions)
Inverse Function Property: f(f⁻¹(x)) = x and f⁻¹(f(x)) = x

Suitable Grade Level

Grades 10-12