Math Problem Statement

Graph each function and its inverse relation on the same set of axes. Determine whether the inverse relation is a function. a) f(x) = x^2 - 4 b) g(x) = 2^x

Solution

Let's work through both parts of this problem:

a) f(x)=x24f(x) = x^2 - 4

  1. Finding the inverse of f(x)f(x):
    • To find the inverse, replace f(x)f(x) with yy: y=x24y = x^2 - 4

    • Swap xx and yy and solve for yy: x=y24x = y^2 - 4 y2=x+4y^2 = x + 4 y=±x+4y = \pm \sqrt{x + 4} Thus, the inverse relation of f(x)f(x) is f1(x)=±x+4f^{-1}(x) = \pm \sqrt{x + 4}.

    • Graphing:

      • The original function f(x)=x24f(x) = x^2 - 4 is a parabola opening upwards, with a vertex at (0,4)(0, -4).
      • The inverse relation f1(x)=±x+4f^{-1}(x) = \pm \sqrt{x + 4} is not a function, since it gives two values (positive and negative square roots) for each xx, except when x=4x = -4.
    • Is the inverse a function? No, the inverse is not a function because it does not pass the vertical line test (it provides two outputs for one input).


b) g(x)=2xg(x) = 2^x

  1. Finding the inverse of g(x)g(x):
    • Replace g(x)g(x) with yy: y=2xy = 2^x

    • Swap xx and yy, and solve for yy: x=2yx = 2^y y=log2(x)y = \log_2(x) Thus, the inverse function is g1(x)=log2(x)g^{-1}(x) = \log_2(x).

    • Graphing:

      • The original function g(x)=2xg(x) = 2^x is an exponential curve that increases rapidly for positive xx and approaches zero as xx becomes more negative.
      • The inverse function g1(x)=log2(x)g^{-1}(x) = \log_2(x) is a logarithmic curve that grows slowly for larger values of xx and is undefined for x0x \leq 0.
    • Is the inverse a function? Yes, the inverse of g(x)g(x) is a function because it passes the vertical line test.


Do you need help with a graphical representation, or do you have any specific questions about the solutions?

Here are 5 questions to further your understanding:

  1. What does the vertical line test indicate about a relation being a function?
  2. How do we algebraically find the inverse of a quadratic function?
  3. Why is the inverse of an exponential function always a logarithmic function?
  4. What restrictions exist on the domain of f(x)=x24f(x) = x^2 - 4 and its inverse?
  5. Can every function have an inverse that is also a function? Why or why not?

Tip: Always check if the inverse relation is a function by applying the vertical line test to its graph.

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Math Problem Analysis

Mathematical Concepts

Functions
Inverse Functions
Graphing

Formulas

f(x) = x^2 - 4
g(x) = 2^x
Inverse Function: swap x and y, solve for y
f^{-1}(x) = ±√(x + 4)
g^{-1}(x) = log_2(x)

Theorems

Vertical Line Test
Properties of Inverse Functions

Suitable Grade Level

Grades 10-12