Math Problem Statement

The functions f(x) = 5x^2 - 10x + 7 where x ≥ 1 and g(x) = 7x - 6 are given. Express the inverse function f^(-1)(x) in the form f^(-1)(x) = ...

Solution

The image shows two functions f(x)f(x) and g(g)g(g), along with the task to express the inverse of ff, i.e., f1(x)f^{-1}(x).

The function f(x)=5x210x+7f(x) = 5x^2 - 10x + 7 is defined for x1x \geq 1, and you are asked to find the inverse of this function f1(x)f^{-1}(x).

Steps to Find the Inverse f1(x)f^{-1}(x):

  1. Set y=f(x)y = f(x): y=5x210x+7y = 5x^2 - 10x + 7

  2. Solve for xx in terms of yy: Rearrange the equation to express xx in terms of yy. First, isolate the quadratic part: 5x210x+7=y5x^2 - 10x + 7 = y 5x210x+(7y)=05x^2 - 10x + (7 - y) = 0

  3. Apply the quadratic formula: For a quadratic equation ax2+bx+c=0ax^2 + bx + c = 0, the solutions for xx are: x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} Here, a=5a = 5, b=10b = -10, and c=7yc = 7 - y. Plug these into the quadratic formula: x=(10)±(10)24(5)(7y)2(5)x = \frac{-(-10) \pm \sqrt{(-10)^2 - 4(5)(7 - y)}}{2(5)} x=10±10020(7y)10x = \frac{10 \pm \sqrt{100 - 20(7 - y)}}{10} x=10±100140+20y10x = \frac{10 \pm \sqrt{100 - 140 + 20y}}{10} x=10±20y4010x = \frac{10 \pm \sqrt{20y - 40}}{10} x=10±25y1010x = \frac{10 \pm 2\sqrt{5y - 10}}{10} x=1±5y105x = 1 \pm \frac{\sqrt{5y - 10}}{5}

  4. Choose the positive root: Since x1x \geq 1, we select the positive root: x=1+5y105x = 1 + \frac{\sqrt{5y - 10}}{5}

  5. Substitute yy with xx to find f1(x)f^{-1}(x): f1(x)=1+5x105f^{-1}(x) = 1 + \frac{\sqrt{5x - 10}}{5}

Thus, the inverse function is: f1(x)=1+5x105f^{-1}(x) = 1 + \frac{\sqrt{5x - 10}}{5}

Would you like further details on any step or an explanation of how this solution was derived?

Here are 5 related questions for deeper understanding:

  1. How do you verify if two functions are inverses of each other?
  2. What happens if we choose the negative root instead of the positive one when finding the inverse?
  3. How can we determine the domain of an inverse function?
  4. How does restricting the domain of a quadratic function help in finding its inverse?
  5. Can every quadratic function have an inverse?

Tip: When dealing with quadratic functions, always check if the domain allows the function to be one-to-one before finding its inverse.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Inverse Functions

Formulas

Quadratic Formula: x = (-b ± √(b² - 4ac)) / 2a
Inverse Function

Theorems

Quadratic Formula
Inverse Function Theorem

Suitable Grade Level

High School (Grades 10-12)