Math Problem Statement

Given the function f(x) = 3^x, graph the transformation g(x) = -f(-x) + 8, including the horizontal asymptote. Plot two points and the horizontal asymptote.

Solution

We are tasked with graphing the transformation of the function f(x)=3xf(x) = 3^x into g(x)=f(x)+8g(x) = -f(-x) + 8, which translates to:

g(x)=3x+8g(x) = -3^{-x} + 8

This involves several transformations. Let’s break it down step by step:


1. Original Function: f(x)=3xf(x) = 3^x

  • This is a standard exponential function that grows rapidly as xx increases.
  • The horizontal asymptote is at y=0y = 0.

2. Transformation Analysis:

  • Reflection over the yy-axis (x-x):
    Changing xx to x-x reflects the graph horizontally, giving 3x3^{-x}.

  • Reflection over the xx-axis (f-f):
    Adding a negative sign before the function reflects the graph vertically. This produces 3x-3^{-x}.

  • Vertical Translation Upward (+8+8):
    Adding +8+8 shifts the entire graph 8 units upward. This changes the horizontal asymptote to y=8y = 8.


3. Key Features of g(x)=3x+8g(x) = -3^{-x} + 8:

  • Horizontal Asymptote: y=8y = 8 (the graph will approach but never touch this line).
  • Behavior:
    • As xx \to \infty, 3x03^{-x} \to 0 so g(x)8g(x) \to 8.
    • As xx \to -\infty, 3x3^{-x} \to \infty, so g(x)g(x) \to -\infty.

4. Points to Plot:

To confirm the graph, calculate two key points:

  1. At x=0x = 0: g(0)=30+8=1+8=7g(0) = -3^{-0} + 8 = -1 + 8 = 7 So, (0,7)(0, 7).

  2. At x=1x = -1: g(1)=3(1)+8=31+8=3+8=5g(-1) = -3^{-(-1)} + 8 = -3^1 + 8 = -3 + 8 = 5 So, (1,5)(-1, 5).


Final Steps:

  • Plot the points: (0,7)(0, 7) and (1,5)(-1, 5).
  • Draw the horizontal asymptote: y=8y = 8.
  • Sketch the reflected, translated curve: It will slope downward as xx \to -\infty and approach y=8y = 8 as xx \to \infty.

Let me know if you want further clarification or need me to illustrate more steps.


Related Questions:

  1. What is the horizontal asymptote of an exponential function after transformations?
  2. How do reflections affect exponential functions like 3x3^x?
  3. How do you determine key points on a transformed exponential graph?
  4. What role does vertical translation play in graphing g(x)g(x)?
  5. How do transformations interact (order of operations) for exponential graphs?

Tip: Always apply reflections and translations step by step to avoid errors in graphing!

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Math Problem Analysis

Mathematical Concepts

Exponential Functions
Function Transformations
Reflections
Vertical Translations
Asymptotes

Formulas

f(x) = 3^x
g(x) = -f(-x) + 8

Theorems

Transformation Rules for Exponential Functions

Suitable Grade Level

Grades 9-11