Discovering Surjective and Non-Injective Functions in Function Theory

In summary, there are different types of functions from the set of natural numbers to itself, such as bijective, injective but not surjective, surjective but not injective, and neither injective nor surjective. Examples of these functions include f(n) = n, f(n) = 2n and f(n) = floor(n/2). These are well-known examples and can be used to determine the properties of a given function.
  • #1
philosophking
175
0
Please help me. I'm trying to find functions where f:N-->N (the set of natural numbers to the set of natural numbers), such that:

f is surjective but not injective,
f is neither surjective nor injective

I'm really not sure how to determine these. Thanks for your consideration.
 
Physics news on Phys.org
  • #2
errr... now that I look back at my other answers ( i had to find one that is bijective and one that is not surjective but injective), i don't even know if those are right.

For bijective, could you have f(n) = n ?
For injective but not surjective, could you have f(n) = 2n + 1 ?

I'm so confused.
 
  • #3
OK hehe i think i figured some stuff out, for my first original question, f(n) = (n-5) + 2 works. But I still need help on my last question! please!

Also, the most recent two questions i asked can be disregarded... haha wow sorry if i confused anyone
 
  • #4
f: N -> N

If f(n) = n, f is bijective.
If f(n) = 2n, f is injective but not surjective (2n+1 also works).
If f(n) = floor(n/2), f is surjective but not injective.
If f(n) = constant, f is neither injective nor surjective.

I think these are all pretty well-known examples.
 
  • #5
thanks, much appreciated
 

1. What is function theory?

Function theory is a branch of mathematics that studies the relationships between input values and output values in mathematical expressions or equations. It is concerned with understanding and analyzing how functions work and how they can be manipulated to solve mathematical problems.

2. What are the main concepts in function theory?

The main concepts in function theory include domain and range, function composition, inverse functions, and transformations. These concepts are essential in understanding the behavior and properties of functions and how they can be used to solve mathematical problems.

3. How is function theory applied in real life?

Function theory has many practical applications in real life, such as in engineering, physics, economics, and computer science. It is used to model and analyze real-world phenomena, make predictions, and solve problems in various fields.

4. What are the common methods used in function theory?

The most common methods used in function theory include graphical representation, algebraic manipulation, and calculus techniques such as differentiation and integration. These methods are used to analyze and solve functions in different forms and to understand their properties and behavior.

5. What are the benefits of studying function theory?

Studying function theory helps develop critical thinking and problem-solving skills, which are essential in many fields. It also provides a foundation for understanding more advanced mathematical concepts and applications. Additionally, it has practical applications in various industries and can be used to make informed decisions and predictions based on data and mathematical models.

Similar threads

  • Precalculus Mathematics Homework Help
Replies
4
Views
2K
  • Set Theory, Logic, Probability, Statistics
Replies
19
Views
2K
  • Set Theory, Logic, Probability, Statistics
Replies
10
Views
3K
  • Topology and Analysis
Replies
8
Views
1K
  • Set Theory, Logic, Probability, Statistics
Replies
1
Views
2K
  • Set Theory, Logic, Probability, Statistics
Replies
2
Views
13K
  • Set Theory, Logic, Probability, Statistics
Replies
9
Views
2K
  • Set Theory, Logic, Probability, Statistics
Replies
13
Views
3K
  • Set Theory, Logic, Probability, Statistics
Replies
2
Views
1K
  • Set Theory, Logic, Probability, Statistics
Replies
1
Views
1K
Back
Top