Suppose we are given 4 sets A, B, C, D such that A ⊆ B and C ⊆ D such that A and C have no elements in common. Prove or give a counterexample to the assertion that A and D also have no elements in common.​

Respuesta :

Here's a counterexample: let

[tex] B = \{1, 2, 3, 4, 5\},\quad D = \{A, B, C, D, 5\}[/tex]

We choose the subsets as follows:

[tex]A = \{1, 5\},\quad C = \{A, B, C\}[/tex]

It is true that [tex]A\subseteq B[/tex] and [tex]C\subseteq D[/tex] and that [tex]A\cap C=\emptyset[/tex], but [tex]A\cap D = \{5\}[/tex]

From the sample sets I used, I have given a counterexample to the assertion that A and D have no elements in common because it was proven that;

A ∩ C = Ø

A ∩ D =  {5}

  • This is about sets notation.

We are told that there are 4 sets namely; A, B, C & D.

We are told that; A ⊆ B and C ⊆ D.

The symbol means Subset.

Therefore set A is a subset of set B and set C is a subset of set D.

  • Now, we are told that those 4 given sets are subsets in such a way that set A and set C have no elements in common. We want to refute the theory that Set A and set D have no elements in common.

  • Let's give some set example as;

Set A = {1, 2, 5}

Set B = {1, 2, 3, 4, 5}

Set C = {6, 7, 8}

Set D = {5, 6, 7, 8, 9}

  • From these sample sets, we can see that;

A ∩ C = Ø

However, A ∩ D =  {5}

  • Since we have proved that A and D have elements in common, it means we have been able to give a counterexample to the assertion that A and D have no elements in common.

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