Math Problem Statement

Graph g(x) = x^2 - 2x for x ≥ 1, and its inverse function.

Solution

To graph the function g(x)=x22xg(x) = x^2 - 2x for x1x \geq 1 and its inverse, let's proceed step by step.

1. Graphing the Function g(x)=x22xg(x) = x^2 - 2x:

This is a quadratic function. We can rewrite it as: g(x)=x22x=(x1)21g(x) = x^2 - 2x = (x - 1)^2 - 1 This is in vertex form, with the vertex at (1,1)(1, -1). For x1x \geq 1, this parabola opens upwards and starts from the vertex (1,1)(1, -1).

Steps to graph:

  • Vertex: (1,1)(1, -1)
  • Shape: Since the coefficient of x2x^2 is positive, the parabola opens upwards.
  • Key Points:
    • At x=1x = 1, g(1)=1g(1) = -1 (the vertex).
    • At x=2x = 2, g(2)=0g(2) = 0.
    • At x=3x = 3, g(3)=3g(3) = 3, and so on.

2. Finding the Inverse:

To find the inverse of g(x)=x22xg(x) = x^2 - 2x for x1x \geq 1, follow these steps:

  1. Start by replacing g(x)g(x) with yy: y=x22xy = x^2 - 2x
  2. Solve for xx in terms of yy. First, complete the square on the right-hand side: y=(x1)21y = (x - 1)^2 - 1 y+1=(x1)2y + 1 = (x - 1)^2 x1=±y+1x - 1 = \pm \sqrt{y + 1} Since x1x \geq 1, we take the positive square root: x=1+y+1x = 1 + \sqrt{y + 1} Therefore, the inverse function is: g1(y)=1+y+1g^{-1}(y) = 1 + \sqrt{y + 1}

3. Graphing the Inverse:

The inverse function g1(x)=1+x+1g^{-1}(x) = 1 + \sqrt{x + 1} is a square root function that starts at (x=1,y=1)(x = -1, y = 1) and increases as xx increases.

Steps to graph:

  • Start Point: (1,1)(-1, 1) (the reflection of the vertex of the original function).
  • Shape: The square root function gradually increases as xx increases.
  • Key Points:
    • At x=0x = 0, g1(0)=2g^{-1}(0) = 2.
    • At x=3x = 3, g1(3)=3g^{-1}(3) = 3, and so on.

Both graphs should be symmetric across the line y=xy = x.

Would you like me to graph this for you? Let me know if you need more details.

Here are some related questions to explore:

  1. What is the domain and range of g(x)g(x) and its inverse?
  2. How would the graph of g(x)g(x) change if the domain restriction were lifted?
  3. Why is it important to consider the domain x1x \geq 1 when finding the inverse of a quadratic function?
  4. Can you verify that the inverse function g1(x)g^{-1}(x) and the original function g(x)g(x) are truly inverses algebraically?
  5. How does the process of completing the square help in finding the inverse of a quadratic function?

Tip: Always remember that the graph of a function and its inverse are reflections across the line y=xy = x.

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Inverse Functions
Graphing

Formulas

g(x) = x^2 - 2x
Inverse of a function by solving y = f(x) for x

Theorems

Quadratic formula
Method of completing the square

Suitable Grade Level

Grades 10-12