Math Problem Statement

Give the graph of one and only one function which satisfies all the following conditions: a. Domain of the function [-5, 0) ∪ (0, ∞) b. The function is continuous on its domain c. f(-5) = f(5) d. lim x→5 f(x) = 6 e. lim x→0⁻ f(x) = ∞ f. lim x→0⁺ f(x) = 0 g. lim x→∞ f(x) = -∞ Explain why the graph of a function which satisfies all these conditions must intercept the x-axis, meaning that there is at least one number c so that f(c) = 0.

Solution

To address this question, let’s analyze the function requirements step by step:


1. Domain

The function's domain is:
[5,0)(0,)[-5, 0) \cup (0, \infty)
This means:

  • The function is defined on two disjoint intervals: [5,0)[-5, 0) (from 5-5 to 00, not including 00) and (0,)(0, \infty) (from 00 onward, not including 00).
  • x=0x = 0 is not in the domain.

2. Continuity

The function is continuous on its domain, so:

  • No jumps, breaks, or holes within [5,0)[-5, 0) and (0,)(0, \infty).
  • However, the function is not defined at x=0x = 0, so no continuity there.

3. Symmetry Condition

f(5)=f(5)f(-5) = f(5):

  • This implies that at x=5x = -5 and x=5x = 5, the function values are equal.

4. Limit Conditions

  • At x5x \to 5:
    limx5f(x)=6\lim_{x \to 5} f(x) = 6
    As xx approaches 55, the function value approaches 66.

  • At x0x \to 0^- (from the left of 00):
    limx0f(x)=\lim_{x \to 0^-} f(x) = \infty
    This indicates a vertical asymptote at x=0x = 0 from the left side.

  • At x0+x \to 0^+ (from the right of 00):
    limx0+f(x)=0\lim_{x \to 0^+} f(x) = 0
    The function value approaches 00 as xx nears 00 from the right side.

  • As xx \to \infty:
    limxf(x)=\lim_{x \to \infty} f(x) = -\infty
    The function decreases unboundedly as xx increases without limit.


5. Graph Intercepts the x-Axis

The final question asks why the graph must intersect the xx-axis, meaning there exists a point cc such that f(c)=0f(c) = 0.

  • As x0+x \to 0^+, the function approaches 00, so it gets arbitrarily close to the x-axis.
  • Since the function is continuous on (0,)(0, \infty) and decreases to -\infty as xx \to \infty, by the Intermediate Value Theorem:
    • On some interval (a,)(a, \infty), where aa is close to 00, the function must cross the xx-axis at least once.
    • This guarantees a c>0c > 0 where f(c)=0f(c) = 0.

6. Summary of Key Points

The function’s graph:

  • Has a vertical asymptote at x=0x = 0.
  • Approaches 66 at x=5x = 5.
  • Decreases to -\infty as xx \to \infty.
  • Must cross the xx-axis due to the behavior described by the Intermediate Value Theorem.

Would you like me to sketch the graph or clarify any step further?


5 Related Questions:

  1. What is the Intermediate Value Theorem, and how does it ensure f(c)=0f(c) = 0?
  2. How does a vertical asymptote affect the continuity of a function at x=0x = 0?
  3. Can there be more than one xx-intercept for the function described above?
  4. How does the limit limxf(x)=\lim_{x \to \infty} f(x) = -\infty affect the graph?
  5. Why does the condition f(5)=f(5)f(-5) = f(5) suggest symmetry at those points?

Tip:

When analyzing limit behavior at critical points (like 00 here), pay close attention to the direction of approach (left-hand and right-hand limits).

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Math Problem Analysis

Mathematical Concepts

Limits
Continuity
Domain and Range
Intermediate Value Theorem
Behavior at Infinity

Formulas

lim x→c f(x)
Intermediate Value Theorem: If f is continuous on [a, b] and f(a) < 0 < f(b), then ∃ c ∈ (a, b) such that f(c) = 0.

Theorems

Intermediate Value Theorem

Suitable Grade Level

College Calculus I