Math Problem Statement

Based on the information conveyed in Figure 5(B), find values of c, L, ε, and δ > 0 such that the following statement holds: If 0 < |x - c| < δ, then |f(x) - L| < ε.

Solution

The image contains two graphs labeled (A) and (B) that depict the function y=f(x)y = f(x), each showing how close the function is to a certain limit. The task is to find values for cc, LL, ϵ\epsilon, and δ\delta such that the following holds:

If 0<xc<δ, then f(x)L<ϵ.\text{If } 0 < |x - c| < \delta, \text{ then } |f(x) - L| < \epsilon.

This is the formal definition of the limit limxcf(x)=L\lim_{x \to c} f(x) = L, with ϵ\epsilon and δ\delta representing how close the function values are to the limit LL when xx is within δ\delta of cc.

For Graph (A):

  • The function f(x)f(x) approaches L=4L = 4 as x0x \to 0.
  • You can choose c=0c = 0, since the vertical line is around x=0x = 0.
  • The values of ϵ\epsilon can be chosen based on the vertical distance between f(x)f(x) and L=4L = 4. From the graph, f(x)f(x) stays between 3.5 and 4.8, so an appropriate ϵ\epsilon could be 0.5.
  • For δ\delta, the horizontal distance between x=0x = 0 and the points where f(x)f(x) starts to deviate from the bounds of ϵ\epsilon gives δ0.1\delta \approx 0.1, since the graph remains within f(x)L<ϵ|f(x) - L| < \epsilon for 0.1<x<0.1-0.1 < x < 0.1.

For Graph (B):

  • The function f(x)f(x) approaches L=10L = 10 as x3x \to 3.
  • You can choose c=3c = 3, since the vertical line is around x=3x = 3.
  • The values of ϵ\epsilon can be chosen based on the vertical distance between f(x)f(x) and L=10L = 10. From the graph, f(x)f(x) stays between 9.8 and 10.4, so an appropriate ϵ\epsilon could be 0.2.
  • For δ\delta, the horizontal distance between x=3x = 3 and the points where f(x)f(x) starts to deviate from the bounds of ϵ\epsilon gives δ0.1\delta \approx 0.1, since the graph remains within f(x)L<ϵ|f(x) - L| < \epsilon for 2.9<x<3.12.9 < x < 3.1.

Would you like more detailed explanations or have any specific questions about this?

Here are 5 follow-up questions:

  1. What does the formal definition of a limit represent graphically?
  2. How would you select different values for δ\delta if the graph changed?
  3. What happens when xc|x - c| becomes greater than δ\delta?
  4. Can ϵ\epsilon be smaller than the chosen values in the graphs? Why or why not?
  5. How do you interpret f(x)f(x) approaching LL as xcx \to c?

Tip: When choosing ϵ\epsilon and δ\delta, visualize the vertical and horizontal distances that limit how far f(x)f(x) can vary from the limit LL.

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Math Problem Analysis

Mathematical Concepts

Limits
Continuity
Epsilon-Delta Definition

Formulas

0 < |x - c| < δ implies |f(x) - L| < ε

Theorems

Epsilon-Delta Definition of Limits

Suitable Grade Level

Undergraduate Calculus