Math Problem Statement

Let f be the piecewise function given by f(x) = {4 - x^2 for x < 4, x + 4 for x >= 4}. Let g be an unknown function with domain (-∞,∞). Which of the following is equal to the one-sided limit lim(x -> 4^-) g(f(x))?

Solution

Let's analyze the problem step by step:

  1. Piecewise function f(x)f(x) is defined as:

    \begin{cases} 4 - x^2 & \text{for } x < 4 \\ x + 4 & \text{for } x \geq 4 \end{cases}$$
  2. We are tasked with finding the one-sided limit: limx4g(f(x)).\lim_{x \to 4^-} g(f(x)).

  3. To solve this, we need to evaluate f(x)f(x) as xx approaches 4 from the left (x4x \to 4^-).

    • For x<4x < 4, f(x)=4x2f(x) = 4 - x^2.
    • Let's compute limx4f(x)\lim_{x \to 4^-} f(x): limx4(4x2)=4(42)=416=12.\lim_{x \to 4^-} (4 - x^2) = 4 - (4^2) = 4 - 16 = -12. So, limx4f(x)=12\lim_{x \to 4^-} f(x) = -12.
  4. Now, we need to find: limx4g(f(x))=limx4g(12)=g(12).\lim_{x \to 4^-} g(f(x)) = \lim_{x \to 4^-} g(-12) = g(-12).

  5. The problem asks which of the given limits matches g(12)g(-12), and we can see that the correct choice corresponds to: limx12+g(x),\lim_{x \to -12^+} g(x), because we are looking at the right-sided limit of g(x)g(x) as x12+x \to -12^+.

Thus, the correct answer is Option E: limx12+g(x).\lim_{x \to -12^+} g(x).

Would you like further details or have any questions?

Here are five related questions to explore further:

  1. What is a piecewise function, and how do limits work for such functions?
  2. How do one-sided limits differ from two-sided limits?
  3. How can we compute limits involving composite functions, like g(f(x))g(f(x))?
  4. What is the geometric interpretation of limits for piecewise-defined functions?
  5. Why is continuity important when evaluating limits?

Tip: When working with piecewise functions, always check which piece is relevant for the point where you're taking the limit.

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Math Problem Analysis

Mathematical Concepts

Piecewise Functions
Limits
Composite Functions

Formulas

lim(x -> 4^-) f(x)
lim(x -> 4^-) g(f(x))

Theorems

Limit Theorem
One-Sided Limits

Suitable Grade Level

Grade 12, Early College