Evaluating Limits: Understanding the Definition and Common Misconceptions

  • Thread starter appplejack
  • Start date
  • Tags
    Limit
In summary, the limit of f(x) as x approaches 2 is 1, not 3 as initially thought, because the definition of a limit only considers the value of f(x) as x gets close to 2, not equal to 2. This understanding may have been the source of confusion.
  • #1
appplejack
43
0

Homework Statement


Evaluate the limits
lim x->2 f(x) if f(x) = 3, x an integer, or 1, otherwise.


Homework Equations





The Attempt at a Solution


I just 3 was the answer because I thought 2 is an integer and if x is an integer then the answer is 3. I was rather shocked to find that the answer is 1. I understand the definition of limits but I think I'm obviously mistaken about something. Thanks.
 
Physics news on Phys.org
  • #2
appplejack said:

Homework Statement


Evaluate the limits
lim x->2 f(x) if f(x) = 3, x an integer, or 1, otherwise.

The Attempt at a Solution


I just 3 was the answer because I thought 2 is an integer and if x is an integer then the answer is 3. I was rather shocked to find that the answer is 1. I understand the definition of limits but I think I'm obviously mistaken about something. Thanks.
If you're shocked by that limit, then it's clear that you don't understand the definition of limits.
 
  • #3
What is your intuitive understanding of what a limit is, appplejack?
 
  • #4
lim x->c f(x)=L
as 'x' approaches c 'a number' from both sides (-,+) and F(x)= approaches L from both side (-,+).
 
Last edited:
  • #5
appplejack said:
lim x->c f(x)=L
as 'x' approaches c 'a number' from both sides (-,+) and F(x)= approaches L from both side (-,+).

That's about right. But the definition of a limit doesn't say anything about the value of f(c) does it? It just talks about the value of f(x) where x is 'close to c'. Not equal to c.
 

FAQ: Evaluating Limits: Understanding the Definition and Common Misconceptions

What is the definition of a limit?

A limit is a mathematical concept that describes the behavior of a function as the input approaches a certain value or point. It represents the value that the function is approaching, or the value that the function gets closer and closer to, as the input gets closer and closer to a specific value.

How do you evaluate a limit?

To evaluate a limit, you can use various techniques such as direct substitution, factoring, or algebraic manipulation. You can also use the properties of limits, such as the sum, difference, product, and quotient rules, to evaluate more complex limits.

What is a one-sided limit?

A one-sided limit, also known as a unilateral limit, is a limit where the input approaches the specified point from only one direction. It is written as either f(x) → L as x approaches a+, or f(x) → L as x approaches a-. This is different from a two-sided limit, where the input approaches the specified point from both the left and the right.

What is a limit at infinity?

A limit at infinity is a special type of limit where the input approaches positive or negative infinity. It is written as either f(x) → L as x approaches positive infinity, or f(x) → L as x approaches negative infinity. This type of limit is used to describe the long-term behavior of a function as the input gets larger or smaller without bound.

Why are limits important in mathematics?

Limits are important in mathematics because they help us understand the behavior of a function and its graph. They are used to define continuity, derivatives, and integrals, which are fundamental concepts in calculus. Limits are also used in many other areas of mathematics, such as in the study of sequences and series, and in the analysis of functions and their properties.

Similar threads

Replies
19
Views
2K
Replies
2
Views
1K
Replies
2
Views
1K
Replies
13
Views
3K
Replies
2
Views
874
Back
Top