Math Problem Statement

Given that lim (4x − 4) = 4 as x approaches 2, illustrate the definition of a limit by finding the largest values of δ that correspond to ε = 0.5, ε = 0.1, and ε = 0.05.

Solution

The problem you uploaded asks to use the formal definition of a limit to find the largest values of δ\delta that correspond to the given ϵ\epsilon values for the limit

limx2(4x4)=4.\lim_{{x \to 2}} (4x - 4) = 4.

Step-by-Step Solution:

We know from the definition of a limit that for any ϵ>0\epsilon > 0, there exists a δ>0\delta > 0 such that:

0<x2<δ    (4x4)4<ϵ.0 < |x - 2| < \delta \implies |(4x - 4) - 4| < \epsilon.

Step 1: Simplifying the Expression

Start by simplifying (4x4)4|(4x - 4) - 4|:

(4x4)4=4x8=4x2.|(4x - 4) - 4| = |4x - 8| = 4|x - 2|.

So, the inequality becomes:

4x2<ϵ.4|x - 2| < \epsilon.

Step 2: Solving for δ\delta

We want to solve for δ\delta. Since 4x2<ϵ4|x - 2| < \epsilon, divide both sides of the inequality by 4:

x2<ϵ4.|x - 2| < \frac{\epsilon}{4}.

Therefore, we can choose δ=ϵ4\delta = \frac{\epsilon}{4}. This means that for each ϵ\epsilon, the corresponding δ\delta is ϵ4\frac{\epsilon}{4}.

Step 3: Calculating δ\delta for each ϵ\epsilon

  • For ϵ=0.5\epsilon = 0.5: δ=0.54=0.125.\delta = \frac{0.5}{4} = 0.125.

  • For ϵ=0.1\epsilon = 0.1: δ=0.14=0.025.\delta = \frac{0.1}{4} = 0.025.

  • For ϵ=0.05\epsilon = 0.05: δ=0.054=0.0125.\delta = \frac{0.05}{4} = 0.0125.

Final Results:

  • For ϵ=0.5\epsilon = 0.5, δ0.125\delta \leq 0.125.
  • For ϵ=0.1\epsilon = 0.1, δ0.025\delta \leq 0.025.
  • For ϵ=0.05\epsilon = 0.05, δ0.0125\delta \leq 0.0125.

Would you like more detailed steps or have any questions?


Here are 5 related questions to expand on the topic:

  1. How does the formal definition of a limit differ from the intuitive definition?
  2. Why is it important to express limits in terms of ϵ\epsilon and δ\delta?
  3. How can this process be applied to functions that are not linear?
  4. How would you find δ\delta if the limit expression had a higher degree polynomial?
  5. Can δ\delta ever be larger than the ϵ\epsilon given?

Tip: When dealing with limits, always ensure to simplify the expression as much as possible before solving for δ\delta.

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Math Problem Analysis

Mathematical Concepts

Limits
Epsilon-Delta Definition
Algebra

Formulas

|x - a| < δ implies |f(x) - L| < ε
f(x) = 4x - 4

Theorems

Epsilon-Delta Definition of Limits

Suitable Grade Level

Grades 11-12, College Introductory Calculus