Math Problem Statement

Graph the logarithmic function: g(x) = 2log_3(x + 4) - 1. Plot two points on the graph of the function, and also draw the asymptote.

Solution

The problem involves graphing the logarithmic function:
g(x)=2log3(x+4)1g(x) = 2 \log_3(x + 4) - 1

Let me break this down step by step so you can graph it:


1. Identify key components of the function:

  • Parent Function: The parent function is log3(x)\log_3(x).
    This function has a vertical asymptote at x=0x = 0 and passes through (1,0)(1, 0) since log3(1)=0\log_3(1) = 0.

  • Transformations:

    • (x+4)(x + 4): This shifts the graph 4 units to the left. So, the vertical asymptote moves to x=4x = -4.
    • 22: This stretches the graph vertically by a factor of 2.
    • 1-1: This shifts the graph 1 unit downward.

2. Plotting points:

To graph, we need at least two points.

  • First, rewrite the function for calculations:
    g(x)=2log3(x+4)1g(x) = 2 \log_3(x + 4) - 1

Step 1: Choose xx-values and compute g(x)g(x).

Since log3(y)\log_3(y) is harder to compute, use simple values of x+4x + 4 that make the logarithm easy. For example:

  1. x+4=3x + 4 = 3 (since log3(3)=1\log_3(3) = 1):
    x=1andg(x)=211=1x = -1 \quad \text{and} \quad g(x) = 2 \cdot 1 - 1 = 1
    So, one point is (1,1)(-1, 1).

  2. x+4=9x + 4 = 9 (since log3(9)=2\log_3(9) = 2):
    x=5andg(x)=221=3x = 5 \quad \text{and} \quad g(x) = 2 \cdot 2 - 1 = 3
    So, another point is (5,3)(5, 3).


3. Vertical asymptote:

The vertical asymptote is at x=4x = -4.


4. Sketch the graph:

  1. Plot the two points (1,1)(-1, 1) and (5,3)(5, 3).
  2. Draw the vertical asymptote at x=4x = -4.
  3. Connect the points smoothly, ensuring the curve approaches the vertical asymptote as xx approaches 4-4 from the right.

Would you like help with more details or examples? Let me know! Here are some related questions to explore:


Follow-up Questions:

  1. How do you compute logarithms with bases other than 10 or ee on a calculator?
  2. What are the steps to identify transformations of logarithmic functions?
  3. What happens if the coefficient of the logarithm (like the 2 in this example) changes to a fraction?
  4. How can we determine the domain of this function?
  5. How does changing the base of the logarithm (log3\log_3 to log5\log_5) affect the graph?

Tip:

Always start by identifying the vertical asymptote when graphing logarithmic functions—it helps anchor the transformations.

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Math Problem Analysis

Mathematical Concepts

Logarithmic Functions
Graph Transformations

Formulas

g(x) = 2log_3(x + 4) - 1

Theorems

Properties of Logarithms
Transformations of Functions

Suitable Grade Level

Grades 10-12