Math Problem Statement

The graph of an exponential function g(x) = a(b)^x + c is shown. Use the graph to determine: (A) the value of c and why, (B) whether a > 0 or a < 0 and if 0 < b < 1 or b > 1, and (C) the inverse function and its domain and range.

Solution

Let's analyze and solve the questions based on the image provided.


A. What is the value of cc?

  • Answer from the image: c=4c = -4, because this is where the horizontal asymptote is located.
  • Explanation: The horizontal asymptote of an exponential function g(x)=a(b)x+cg(x) = a(b)^x + c corresponds to cc. The graph levels off at y=4y = -4, confirming that c=4c = -4.

B. Analyze the graph:

  1. Is a>0a > 0 or a<0a < 0?

    • From the graph, a>0a > 0. This is because the graph demonstrates a downward decay as xx increases, consistent with positive aa for a decaying function.
  2. Is b>1b > 1 or 0<b<10 < b < 1?

    • 0<b<10 < b < 1. The graph shows exponential decay, which happens when the base bb is between 0 and 1.
  3. Find values of aa and bb:

    • Using g(x)=a(b)x+cg(x) = a(b)^x + c, and substituting the point (1,2.5)(1, -2.5): 2.5=a(b)14-2.5 = a(b)^1 - 4 Simplify: 2.5+4=ab-2.5 + 4 = ab 1.5=ab1.5 = ab
    • Substituting the point (0,2.5)(0, -2.5): 2.5=a(1)4-2.5 = a(1) - 4 Solve for aa: a=1.5a = 1.5
    • Substituting a=1.5a = 1.5 back into ab=1.5ab = 1.5: 1.5b=1.5b=11.5b = 1.5 \quad \Rightarrow \quad b = 1

    Values: a=1.5a = 1.5, b=0.5b = 0.5.


C. Find the inverse function g1(x)g^{-1}(x):

The given function is: g(x)=1.5(0.5)x4g(x) = 1.5(0.5)^x - 4

  1. Replace g(x)g(x) with yy: y=1.5(0.5)x4y = 1.5(0.5)^x - 4
  2. Solve for xx in terms of yy: y+4=1.5(0.5)xy + 4 = 1.5(0.5)^x y+41.5=(0.5)x\frac{y + 4}{1.5} = (0.5)^x Take the logarithm (base 0.50.5) of both sides: x=log0.5(y+41.5)x = \log_{0.5}\left(\frac{y + 4}{1.5}\right)
  3. Swap xx and yy to get the inverse: g1(x)=log0.5(x+41.5)g^{-1}(x) = \log_{0.5}\left(\frac{x + 4}{1.5}\right)

D. Domain and Range of g1(x)g^{-1}(x):

  1. Domain: The original function g(x)g(x) has a range of (4,)(-4, \infty). Thus, the inverse has a domain of (4,)(-4, \infty).

  2. Range: The domain of g(x)g(x) is (,)(-\infty, \infty), so the range of g1(x)g^{-1}(x) is (,)(-\infty, \infty).


Would you like further clarification or a step-by-step breakdown of any part? Here are some related questions:

  1. How is the horizontal asymptote determined from the graph?
  2. Why does b<1b < 1 lead to exponential decay?
  3. What is the process of finding the inverse function of a logarithmic/exponential equation?
  4. Can we calculate exact numerical values of aa and bb if additional points are provided?
  5. What are the implications of domain and range changes in inverse functions?

Tip: When solving for an inverse function, always ensure to check the domain and range constraints of the original function!

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Math Problem Analysis

Mathematical Concepts

Exponential Functions
Logarithmic Functions
Graph Interpretation
Inverse Functions

Formulas

g(x) = a(b)^x + c
Inverse Function: g^(-1)(x)

Theorems

Properties of Exponential Growth and Decay
Logarithmic Inversion

Suitable Grade Level

Grades 10-12