Math Problem Statement

can you find me the inverse of f(x)=x^2+4x-6

Solution

To find the inverse of the function f(x)=x2+4x6f(x) = x^2 + 4x - 6, we need to follow these steps:

1. Express the function in a form where we can easily solve for xx.

First, rewrite the function:

f(x)=x2+4x6f(x) = x^2 + 4x - 6

Complete the square to rewrite the quadratic in a more convenient form:

x2+4x=(x+2)24x^2 + 4x = (x + 2)^2 - 4

Now substitute this back into the function:

f(x)=(x+2)246=(x+2)210f(x) = (x + 2)^2 - 4 - 6 = (x + 2)^2 - 10

So the function becomes:

f(x)=(x+2)210f(x) = (x + 2)^2 - 10

2. Swap f(x)f(x) with yy and solve for xx.

Let y=(x+2)210y = (x + 2)^2 - 10.

Now, solve for xx in terms of yy:

y+10=(x+2)2y + 10 = (x + 2)^2

Take the square root of both sides:

x+2=±y+10x + 2 = \pm \sqrt{y + 10}

Solve for xx:

x=2±y+10x = -2 \pm \sqrt{y + 10}

3. Choose the correct branch.

Since a function must be one-to-one to have an inverse, we need to restrict the domain of the original function to make it one-to-one. We can either consider the domain x2x \geq -2 (the right half of the parabola) or x2x \leq -2 (the left half of the parabola). For the inverse to be a function, we must choose one branch.

Assuming we restrict to x2x \geq -2, we take the positive square root:

x=2+y+10x = -2 + \sqrt{y + 10}

4. Write the inverse.

Now, replace yy with xx to express the inverse function:

f1(x)=2+x+10f^{-1}(x) = -2 + \sqrt{x + 10}

Final Answer:

The inverse of f(x)=x2+4x6f(x) = x^2 + 4x - 6 (with the domain restricted to x2x \geq -2) is:

f1(x)=2+x+10f^{-1}(x) = -2 + \sqrt{x + 10}


Would you like further clarification on this process, or is there any part you need help with?

Related Questions:

  1. What is the general method for finding the inverse of a quadratic function?
  2. How does completing the square help in solving for the inverse of a quadratic?
  3. Why is it important to restrict the domain of a quadratic function when finding its inverse?
  4. How can we verify the inverse by checking if f(f1(x))=xf(f^{-1}(x)) = x and f1(f(x))=xf^{-1}(f(x)) = x?
  5. What happens if we choose the other branch (the negative square root)?

Tip: Remember that the inverse of a function exists only if the function is one-to-one. For quadratics, this requires restricting the domain.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Functions
Inverse Functions
Completing the Square

Formulas

f(x) = x^2 + 4x - 6
f(x) = (x + 2)^2 - 10
f^{-1}(x) = -2 + sqrt(x + 10)

Theorems

Inverse Function Theorem
One-to-One Function Requirement

Suitable Grade Level

Grades 10-12