Math Problem Statement

Let f(x) = (x + 2)^2. Find a domain on which f is one-to-one and non-decreasing. Find the inverse of f restricted to this domain.

Solution

The given function is f(x)=(x+2)2f(x) = (x + 2)^2.

Part 1: Find a domain where f(x)f(x) is one-to-one and non-decreasing.

  • The function f(x)=(x+2)2f(x) = (x + 2)^2 is a parabola, which is symmetric about x=2x = -2.
  • Parabolas are decreasing to the left of the vertex and increasing to the right. So, to make the function one-to-one, we need to restrict the domain to where the function is either increasing or decreasing.
  • To find a non-decreasing domain, we choose the portion of the function where it increases, which happens to the right of the vertex x=2x = -2. So the domain should be x2x \geq -2.

Thus, the restricted domain is x2x \geq -2.

Part 2: Find the inverse of f(x)f(x) on this restricted domain.

  • To find the inverse, first set y=f(x)=(x+2)2y = f(x) = (x + 2)^2.
  • Solve for xx in terms of yy: y=(x+2)2y = (x + 2)^2 Take the square root of both sides: y=x+2\sqrt{y} = x + 2 Since we are restricting the domain to x2x \geq -2, we take the positive square root: x=y2x = \sqrt{y} - 2
  • Therefore, the inverse function is: f1(x)=x2f^{-1}(x) = \sqrt{x} - 2

Final Answer:

  1. The domain where f(x)f(x) is one-to-one and non-decreasing: x2x \geq -2.
  2. The inverse of f(x)f(x) on this domain: f1(x)=x2f^{-1}(x) = \sqrt{x} - 2.

Would you like more details or have any questions?

Here are 5 related questions to deepen your understanding:

  1. How do you verify that a function is one-to-one on a given domain?
  2. Why is it necessary to restrict the domain of quadratic functions to find an inverse?
  3. What happens if we restrict the domain to x2x \leq -2 instead?
  4. How can you graphically interpret the inverse of a function?
  5. How would you compute the derivative of the inverse function?

Tip: Always verify that a function is one-to-one on the chosen domain before finding its inverse, as functions need to be bijective to have an inverse.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Functions
Inverse Functions
Domain Restrictions

Formulas

f(x) = (x + 2)^2
Inverse: f^{-1}(x) = sqrt(x) - 2

Theorems

A quadratic function is one-to-one on a restricted domain
To find an inverse, the function must be bijective

Suitable Grade Level

Grades 10-12