contestada

For each of the following statements about sets A, B, and C, either prove the statement is true or give a counterexample to show that it is false.
a. If A⊆BA⊆B and B⊆CB⊆C, then A⊆CA⊆C.
b. If A∈BA∈B and B⊆CB⊆C, then A⊆CA⊆C.
c. If A∈BA∈B and B⊆CB⊆C, then A∈CA∈C.
d. If A∈BA∈B and B∈CB∈C, then A∈CA∈C.

Respuesta :

Answer:

a. True

b. False

c. True

d. False

Step-by-step explanation:

a. Meaning

as we can see that x is an element of Y

So notation is

[tex]x \in Y[/tex]

Therefore x is the subset of Y if each of an element of X is also an element of Y.

So notation is

[tex]X \subseteq Y[/tex]

2. (a) We need to proof

When [tex]A \subseteq B and B \subseteq C \so A \subseteq C[/tex]

We will say that A, B and C are the set that is [tex]A\subseteq B\ and\ B\subseteq C[/tex]

When A = ∅ then [tex]A\subseteq C[/tex] which shows true, as the set of empty is a subset of each set.

Hence, it is safe to say that A is not the empty set.

Now we will proof directly

Let us say x be an element of A

[tex]x \in A[/tex]

As [tex]A \subseteq B,[/tex] each of the element of A is also an element of B

[tex]x \in B[/tex]

As [tex]B \subseteq C[/tex], each if the element of B is also an element of C

[tex]x \in C[/tex]

Therefore, as we can see that each of an element of A is also known an element of C, that states [tex]A \subseteq C[/tex]

So, the given statement is true, as we conclude with a proof.

(b). We will assume {1}, B = {{1},2} and C = {{1},2,3}

As in the point a, which is an element of B, that is [tex]A \in B[/tex] which is true

As all of the elements in B are also an element in C, [tex]B \subseteq C[/tex] which is also correct.

Although, [tex]A \subseteq C[/tex] is false as 1 is an element of A that is not in C.

(c) We need to proof

When  [tex]A \in B\ and \ B \subseteq C[/tex] then [tex]A \in C[/tex]

Let us assume that A, B and C are the sets that [tex]A\in B\ and\ B \subseteq C[/tex]

As, [tex]A \in B, \which\ is\ an\ element\ of\ the\ set\ B[/tex]

[tex]A\in B[/tex]

As, [tex]B \subseteq C[/tex], each of the element of B is also an element of C

[tex]A\in C[/tex]

So, its true.

(d) We will assume {1}, B = {{1},2} and C = {{1},2,3}

As in the point a, which is an element of B, that is [tex]A \in B[/tex] which is true

As {{1},2} is an element of B, [tex]B \in C[/tex] is correct

Although [tex]A \in C[/tex] is not correct as {1) is not an element in C.

SO the statement is false

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