Math Problem Statement

Let f(x) = ln(3-x) + 2. Describe how to use function transformation to get from ln(x) to f(x). Then sketch the graph of f(x) by starting with a graph ln(x) and transforming it.

Solution

To describe how to use function transformations to get from ln(x)\ln(x) to f(x)=ln(3x)+2f(x) = \ln(3-x) + 2, we can break down the process into several steps, each corresponding to a standard transformation of the function ln(x)\ln(x).

Step-by-Step Function Transformations

  1. Start with ln(x)\ln(x): This is the basic natural logarithm function with a domain of (0,)(0, \infty).

  2. Horizontal Reflection and Translation ( ln(x)\ln(-x) ):

    • Reflect ln(x)\ln(x) across the yy-axis to get ln(x)\ln(-x).
    • The domain changes to (,0)(-\infty, 0), which includes all negative values of xx.
  3. Horizontal Shift ( ln(3x)\ln(3-x) ):

    • Shift ln(x)\ln(-x) to the right by 3 units. This gives the function ln(3x)\ln(3-x).
    • The domain now changes to (,3)(-\infty, 3), so the function is defined for all xx less than 3.
  4. Vertical Translation ( ln(3x)+2\ln(3-x) + 2 ):

    • Shift ln(3x)\ln(3-x) upward by 2 units. This results in the function f(x)=ln(3x)+2f(x) = \ln(3-x) + 2.

Transformations Summary

  • Reflection: ln(x)\ln(x)ln(x)\ln(-x) (across the yy-axis).
  • Horizontal Shift: ln(x)\ln(-x)ln(3x)\ln(3-x) (right by 3 units).
  • Vertical Shift: ln(3x)\ln(3-x)ln(3x)+2\ln(3-x) + 2 (up by 2 units).

Sketching the Graph of f(x)=ln(3x)+2f(x) = \ln(3-x) + 2

  1. Graph of ln(x)\ln(x):

    • The function ln(x)\ln(x) has a vertical asymptote at x=0x = 0 and increases without bound as xx becomes larger.
    • It passes through (1,0)(1, 0) and approaches -\infty as xx approaches 0 from the right.
  2. Transform to ln(x)\ln(-x):

    • Reflect the graph of ln(x)\ln(x) across the yy-axis.
    • Now there is a vertical asymptote at x=0x = 0, but the function is defined for x<0x < 0.
  3. Transform to ln(3x)\ln(3-x):

    • Shift the graph of ln(x)\ln(-x) 3 units to the right.
    • The vertical asymptote moves to x=3x = 3.
    • The function passes through (2,0)(2, 0) and is defined for x<3x < 3.
  4. Transform to ln(3x)+2\ln(3-x) + 2:

    • Shift the graph of ln(3x)\ln(3-x) upwards by 2 units.
    • Now the vertical asymptote remains at x=3x = 3, and the graph passes through (2,2)(2, 2).
    • The graph approaches 2 as xx becomes very small (approaching -\infty).

Final Graph of f(x)=ln(3x)+2f(x) = \ln(3-x) + 2

  • Domain: (,3)(-\infty, 3)
  • Vertical Asymptote: x=3x = 3
  • Horizontal Shift: Moves right by 3 units.
  • Vertical Shift: Moves up by 2 units.

Would you like a detailed sketch of the graph or have any further questions on this topic?


Here are 5 related questions for further exploration:

  1. What is the range of the function f(x)=ln(3x)+2f(x) = \ln(3-x) + 2?
  2. How would you find the x-intercept of f(x)f(x)?
  3. What is the behavior of f(x)f(x) as xx approaches 3 from the left?
  4. Can you find the inverse of the function f(x)f(x)?
  5. How would you apply transformations if the function were f(x)=ln(3x)+2f(x) = -\ln(3-x) + 2?

Tip: Understanding transformations of the basic logarithmic function is crucial for sketching more complex log functions effectively.

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Math Problem Analysis

Mathematical Concepts

Logarithmic Functions
Function Transformations

Formulas

f(x) = ln(x)
f(x) = ln(3-x) + 2

Theorems

Properties of Logarithmic Functions
Horizontal and Vertical Shifts

Suitable Grade Level

Grades 10-12