Math Problem Statement

What are the features of the function f(x) = -2 log_3 (x + 4) graphed below?

Solution

Let's analyze the function f(x)=2log3(x+4)f(x) = -2 \log_3 (x + 4) and fill in the blanks in the statement provided.

  1. Type of Function: This is a logarithmic function because it involves a logarithm, specifically log3(x+4)\log_3(x + 4).

  2. Asymptote: Logarithmic functions generally have a vertical asymptote where the argument of the logarithm is zero. In this case: x+4=0x=4x + 4 = 0 \Rightarrow x = -4 So, the vertical asymptote is at x=4x = -4.

  3. Range: Since the logarithmic function here is scaled and reflected vertically (due to the 2-2 coefficient), it will produce all real values as f(x)f(x). Thus, the range is (,)(-\infty, \infty).

  4. Monotonicity: The function has a negative coefficient in front of the logarithmic term, which means it will be decreasing over its domain. The function decreases as xx increases from left to right.

  5. Domain: The domain of the function is where the argument of the logarithm is positive: x+4>0x>4x + 4 > 0 \Rightarrow x > -4 So, the domain is (4,)(-4, \infty).

  6. End Behavior:

    • Left Side (approaching x=4x = -4 from the right): As xx approaches 4-4 from the right, f(x)f(x) \to \infty.
    • Right Side (as xx \to \infty): As xx \to \infty, f(x)f(x) \to -\infty because of the negative scaling.

Filling in the Blanks

Using this information, we can fill in the answers:

  • Function Type: Logarithmic
  • Asymptote: Vertical, x=4x = -4
  • Range: (,)(-\infty, \infty)
  • Monotonicity: Decreasing on (4,)(-4, \infty)
  • Left End Behavior: As x4+x \to -4^+, f(x)f(x) \to \infty
  • Right End Behavior: As xx \to \infty, f(x)f(x) \to -\infty

Would you like further details on any of these points?

Here are some additional questions for practice:

  1. How would the graph change if the coefficient were positive instead of negative?
  2. What would be the effect on the domain if we had f(x)=2log3(x4)f(x) = -2 \log_3 (x - 4) instead?
  3. How does the base of the logarithm (33) affect the graph's shape?
  4. Can you find the x-intercept of this function?
  5. What happens to the asymptote if we add a constant outside the logarithm?

Tip: Remember that for a logarithmic function f(x)=logb(x+c)f(x) = \log_b(x + c), the asymptote is always at x=cx = -c.

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Math Problem Analysis

Mathematical Concepts

Logarithmic Functions
Asymptotes
Domain and Range
End Behavior
Monotonicity

Formulas

f(x) = -2 log_3 (x + 4)

Theorems

Properties of Logarithmic Functions

Suitable Grade Level

Grades 11-12