Please check my proof; how many functions exist from X to Y?

In summary, the conversation discussed the number of functions that exist from a set X to a set Y, with the formula m^n being determined as the possible number of functions. It was also noted that for every element in X, there is a unique element in Y that it can be paired with, resulting in n coordinate pairs in the function.
  • #1
SithsNGiggles
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Homework Statement


I just need to know if it makes sense; I was told that I can't have anyone make any improvements on what I've written myself.

Question: If [itex]X = \{ x_1 , \ldots, x_n \}[/itex] and [itex]Y = \{ y_1 , \ldots, y_m \}[/itex], how many functions from [itex]X[/itex] to [itex]Y[/itex] exist?

My answer: [itex]m^n[/itex] functions

The Attempt at a Solution


For any element [itex]x \in X[/itex], there exists a unique [itex]y \in Y[/itex] for which [itex]F(x) = y[/itex].

Every [itex]n[/itex] element in [itex[X[/itex] will be paired with anyone of the [itex]m[/itex] elements in [itex]Y[/itex].
i.e. there exist [itex]m[/itex] possible [itex]F(x_1)[/itex] in [itex]Y[/itex] that can be paired with [itex]x_1[/itex].
[itex]x_2[/itex] can be paired with [itex]m[/itex] possible [itex]F(x_2)[/itex]
[itex]\vdots[/itex]
[itex]x_n[/itex] can be paired with [itex]m[/itex] possible [itex]F(x_n)[/itex].

Because the domain [itex]D_F = X[/itex], every function generated through F will contain [itex]n[/itex] coordinate pairs. Furthermore, since there are [itex]m[/itex] possible values [itex]F(x) = y[/itex] for each element [itex]x[/itex], there are [itex]n[/itex] factors of [itex]m[/itex], or [itex]m^n[/itex], possible functions.

Thanks for any commentary (but not actual help!) you can provide.
 
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  • #2
Makes perfect sense to me.
 

FAQ: Please check my proof; how many functions exist from X to Y?

1. How do you determine the number of functions from X to Y?

The number of functions from X to Y can be determined by using the formula 𝟮^𝒙𝒚, where x is the cardinality (number of elements) of set X and y is the cardinality of set Y. This formula applies when the function is defined as a mapping from every element in X to every element in Y, including the possibility of repeated values.

2. Can there be an infinite number of functions from X to Y?

Yes, there can be an infinite number of functions from X to Y if either set X or set Y has an infinite cardinality. This means that there are an infinite number of possible mappings between the two sets.

3. What is the difference between a one-to-one function and an onto function?

A one-to-one function, also known as an injective function, is a function where each element in the domain (set X) is mapped to a unique element in the codomain (set Y). An onto function, also known as a surjective function, is a function where every element in the codomain (set Y) is mapped to by at least one element in the domain (set X).

4. How does the cardinality of set X impact the number of functions from X to Y?

The cardinality of set X directly impacts the number of functions from X to Y. The larger the cardinality of set X, the larger the possible number of functions from X to Y. This is because each element in X can be mapped to any element in Y, and the more elements in X, the more possible mappings there are.

5. Can the number of functions from X to Y be negative?

No, the number of functions from X to Y cannot be negative. Functions are defined as a relation between two sets where each input (element in X) is mapped to a unique output (element in Y), and the number of functions represents the number of possible mappings. Therefore, the number of functions can only be a non-negative integer.

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