Math Problem Statement

solve only question 14

Find formulas for g_2(x) and g_2^{-1}(x). State the domain and range of each function.

Solution

To solve question 14, we are tasked with finding the formulas for g2(x)g_2(x) and g21(x)g_2^{-1}(x) and stating the domain and range of each function. Let's work through this:

Observing the Graph:

We can see that the given graph is a parabola, y=x2+1y = x^2 + 1, and the functions g1(x)g_1(x), g2(x)g_2(x), and their inverses are also plotted.

For g2(x)g_2(x), it appears to be the lower branch of the parabola, and g21(x)g_2^{-1}(x) is the reflection of g2(x)g_2(x) across the line y=xy = x.

Step-by-Step Solution for g2(x)g_2(x):

1. Formula for g2(x)g_2(x):

Since g2(x)g_2(x) represents the lower branch of the parabola, it must correspond to: g2(x)=x1g_2(x) = -\sqrt{x - 1} This is because the equation y=x2+1y = x^2 + 1 represents the parabola, and the lower branch is obtained by taking the negative square root (inverting the sign).

2. Domain and Range of g2(x)g_2(x):

  • Domain: Since g2(x)=x1g_2(x) = -\sqrt{x - 1}, the expression inside the square root must be non-negative. Therefore, the domain is x1x \geq 1 or [1,)[1, \infty).
  • Range: Because we are taking the negative square root, the values of g2(x)g_2(x) will be non-positive. As x1x \to 1, g2(x)0g_2(x) \to 0, and as xx \to \infty, g2(x)g_2(x) \to -\infty. Therefore, the range is (,0](-\infty, 0].

Step-by-Step Solution for g21(x)g_2^{-1}(x):

1. Formula for g21(x)g_2^{-1}(x):

The inverse function g21(x)g_2^{-1}(x) is found by solving y=x1y = -\sqrt{x - 1} for xx in terms of yy: y=x1    y=x1    x=y2+1y = -\sqrt{x - 1} \implies -y = \sqrt{x - 1} \implies x = y^2 + 1 Thus, g21(x)=x2+1g_2^{-1}(x) = x^2 + 1.

2. Domain and Range of g21(x)g_2^{-1}(x):

  • Domain: The domain of g21(x)g_2^{-1}(x) is the range of g2(x)g_2(x), which is (,0](-\infty, 0].
  • Range: The range of g21(x)g_2^{-1}(x) is the domain of g2(x)g_2(x), which is [1,)[1, \infty).

Final Answer:

  • g2(x)=x1g_2(x) = -\sqrt{x - 1}, with domain [1,)[1, \infty) and range (,0](-\infty, 0].
  • g21(x)=x2+1g_2^{-1}(x) = x^2 + 1, with domain (,0](-\infty, 0] and range [1,)[1, \infty).

Let me know if you want further details or have any questions.

Here are some related questions:

  1. How is the inverse of a function related to its graph?
  2. Why does the lower branch of the parabola correspond to g2(x)g_2(x)?
  3. What is the general process for finding the inverse of a function?
  4. How does the domain of a function relate to the range of its inverse?
  5. What are the conditions for a function to have an inverse?

Tip: Always check if the original function is one-to-one before finding its inverse; otherwise, restrict its domain accordingly.

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Math Problem Analysis

Mathematical Concepts

Algebra
Functions
Inverses of Functions
Quadratic Functions

Formulas

g_2(x) = -√(x - 1)
g_2^{-1}(x) = x^2 + 1

Theorems

Inverse Function Theorem: If f is a one-to-one function, its inverse exists and reflects over the line y = x.

Suitable Grade Level

Grades 11-12