Solving Epsilon-Delta Proof: Homework Statement

In summary, the conversation discusses how to prove a limit using the given equation and steps. The person provides a proof, but is unsure if they have missed something. The other person confirms that the proof is correct and that it proves the limit.
  • #1
appplejack
43
0

Homework Statement


I just want to make sure I include all the steps in doing this:

lim (6x-7) = 11
x->3


Homework Equations





The Attempt at a Solution


given ε>0, we need to find a δ>0, such that 0< lx-3l < δ then 0 < l (6x-7)-11 l < ε
To prove this I need to make 0 < l (6x-7)-11 l < ε look like 0< lx-3l < δ

1. l 6x-18 l < ε = l x-3 l < ε/6

2. let δ = ε/6

3. lx-3l < δ = > lx-3l < ε/6

This still doesn't feel like I proved something but was there something that I missed?
 
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  • #2
What you have proved is that if δ=ε/6 then lx-3l<δ -> |(6x-7)-11|<ε. That should really be your last line. And, yes, that proves your limit.
 

1. What is an Epsilon-Delta Proof?

An Epsilon-Delta Proof is a method used to rigorously prove the limit of a function. It involves using a small positive number, epsilon, and finding a corresponding small positive number, delta, such that when the input to the function is within delta of the limit, the output is within epsilon of the limit.

2. Why are Epsilon-Delta Proofs important?

Epsilon-Delta Proofs are important because they provide a rigorous way to prove the limit of a function. This allows for a deeper understanding of the behavior of functions and provides a solid foundation for many mathematical concepts, such as continuity and differentiability.

3. What is the process for solving an Epsilon-Delta Proof?

The process for solving an Epsilon-Delta Proof involves first setting up the definition of a limit using epsilon and delta, and then using algebraic manipulation and logical reasoning to find the appropriate value of delta for a given epsilon. This often involves finding a suitable bound for the input to the function and using that to determine the corresponding bound for the output.

4. What are some common challenges in solving Epsilon-Delta Proofs?

Some common challenges in solving Epsilon-Delta Proofs include finding a suitable bound for the input to the function, determining the appropriate direction of the inequalities, and recognizing when a proof cannot be completed due to the nature of the function.

5. How can I improve my skills in solving Epsilon-Delta Proofs?

To improve your skills in solving Epsilon-Delta Proofs, it is important to practice regularly and to understand the underlying concepts and techniques involved. It can also be helpful to work through examples and seek guidance from a teacher or tutor when encountering difficult problems.

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