Proving Subset Inclusion for Intersection of Function Images

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In summary, the conversation discusses the proof of two statements: a) f(E ∪ F) ≡ f(E) ∪ f(F) and b) f(E ∩ F) ⊂ f(E) ∩ f(F). The first statement has been solved, but the second one is still being worked on. The conversation ends with one participant asking for clarification on "and so on and so forth" used in the attempted solution.
  • #1
Bipolarity
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Homework Statement



Suppose f: A → B and that E,F are subsets of A.
Prove the following:
a) [itex] f(E \cup F) \equiv f(E) \cup f(F) [/itex]
b) [itex] f(E \cap F) \subset f(E)\cap f(F) [/itex]

Homework Equations



The Attempt at a Solution


So far I have solved the first one, but I am having trouble with the second. I have no idea where to begin.

BiP
 
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  • #2
I don't believe b) is true..
 
  • #3
Woops! Sorry I wrote it wrong. I'll change that.

BiP
 
  • #4
Ok you that should just be a straight element proof then, just follow your nose, if b is in f(E∩F) then there exists an a in E∩F such f(a)=b, if a is in E∩F then a is in E and F.. and so on and so forth.
 
  • #5
What does "and so on and so forth" supposed to mean? I don't understand your proof sorry. It's incomplete.

BiP
 
  • #6
Bipolarity said:
It's incomplete.

Yes, because you are supposed to finish it.
 

1. What is a Union/Intersection Proof?

A Union/Intersection Proof is a type of mathematical proof that demonstrates the relationship between two sets by showing that the union or intersection of the two sets is equal to a third set. It is commonly used in the field of set theory to prove properties about sets.

2. How is a Union/Intersection Proof different from other types of proofs?

Unlike other types of proofs, such as direct proofs or proof by contradiction, a Union/Intersection Proof does not rely on logical arguments or assumptions. Instead, it uses the properties of unions and intersections to show that two sets are equal.

3. What are some common strategies for solving Union/Intersection Proofs?

Some common strategies for solving Union/Intersection Proofs include using Venn diagrams, using set identities and properties, and using logical equivalences. It is also important to carefully define the sets and their elements before attempting to prove their relationship.

4. Can Union/Intersection Proofs be used to prove other types of mathematical statements?

Yes, Union/Intersection Proofs can be used to prove other types of mathematical statements, such as set equalities and inequalities, as well as properties of sets and their elements. They can also be applied to other areas of mathematics, such as calculus and graph theory.

5. Are there any common mistakes to avoid when solving Union/Intersection Proofs?

One common mistake to avoid when solving Union/Intersection Proofs is assuming that the union or intersection of two sets is always commutative or associative. It is important to remember that the order of elements in a set can affect the outcome of the proof. It is also important to carefully consider the definitions and properties of sets before attempting to prove their relationship.

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