Finding Delta for a Given Epsilon and Limit: 3-2x, x0=3, E=.02

In summary, given a function f(x) = 3-2x, a point x0 = 3, and a positive number E = 0.02, the limit as x approaches 3 is equal to -3. To find delta, we can set up the inequality |f(x)-L|<E, which becomes |3-2x-(-3)|<0.02, and simplifies to |6-2x|<0.02. From there, we can solve for x to get -0.01<x<0.01. Plugging this back into the original equation, we get -3.01<f(x)<-2.99, which gives us a delta value of
  • #1
Not An Einstein
2
0
Given a function f(x), a point x0, and a positive number E (epsilon), write the limit then find delta>0 such that for all x 0< |x-x0| < delta -> |f(x)-L| < E
f(x) = 3-2x, x0=3, E=.02
Here is my attempt:
Lim (3-2x) as x->3 = -3
-.02 < |3-2x - 3| <.02
-.02 < |-2x| < .02
.01 > x > -.01
-2.99 > x-3 > -3.01
-2.99 > |x-3|
Delta= -2.99
Is this right? I'm really confused, any help would be greatly appreciated, even just an explanation. Thanks.
 
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  • #3
Not An Einstein said:
Given a function f(x), a point x0, and a positive number E (epsilon), write the limit then find delta>0 such that for all x 0< |x-x0| < delta -> |f(x)-L| < E
f(x) = 3-2x, x0=3, E=.02
Here is my attempt:
Lim (3-2x) as x->3 = -3
-.02 < |3-2x - 3| <.02
-.02 < |-2x| < .02
.01 > x > -.01
-2.99 > x-3 > -3.01
-2.99 > |x-3|
Delta= -2.99
Is this right? I'm really confused, any help would be greatly appreciated, even just an explanation. Thanks.

You started going off track when you wrote |f(x)-L|<E. Since L is -3 that becomes |(3-2x)-(-3)|=|3-2x+3|=|6-2x|<0.02. Try it again from there.
 

1. What is a Delta and Epsilon Proof?

A Delta and Epsilon proof is a mathematical technique used to formally prove the limit of a function. It is commonly used in Calculus and related fields to show that a function approaches a specific value as its input approaches a certain value.

2. How does a Delta and Epsilon Proof work?

A Delta and Epsilon proof involves choosing a small value for delta (denoted as δ) and showing that for any value of epsilon (denoted as ε), there exists a corresponding delta such that the distance between the function's output and the desired limit is less than epsilon whenever the input is within delta of the desired limit. This shows that the function gets arbitrarily close to the desired limit as the input approaches the desired limit.

3. What is the purpose of a Delta and Epsilon Proof?

The purpose of a Delta and Epsilon proof is to provide a rigorous and logical way to prove the limit of a function. It is especially useful in proving properties of continuous functions and in solving problems involving limits in Calculus.

4. Are there any limitations to Delta and Epsilon Proofs?

While Delta and Epsilon proofs are powerful tools in mathematics, they do have some limitations. They can only be used to prove the limit of a function at a specific point, and they may not work for all types of functions. Additionally, Delta and Epsilon proofs can be tedious and time-consuming, requiring careful selection of delta and epsilon values.

5. How can I improve my skills in using Delta and Epsilon Proofs?

The best way to improve your skills in using Delta and Epsilon proofs is through practice. Familiarize yourself with the definitions and properties of limits, and work through a variety of examples and exercises. It can also be helpful to study and understand different proof techniques used in Delta and Epsilon proofs, such as the definition of a limit, the triangle inequality, and the squeeze theorem.

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