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Consider [tex]\( U=\{x \mid x \text{ is a real number} \} \)[/tex].

[tex]\[
\begin{array}{l}
A=\{x \mid x \in U \text{ and } x+2\ \textgreater \ 10\} \\
B=\{x \mid x \in U \text{ and } 2x\ \textgreater \ 10\}
\end{array}
\][/tex]

Which pair of statements is correct?

A. [tex]\( 5 \in A \)[/tex]; [tex]\( 5 \in B \)[/tex]

B. [tex]\( 6 \in A \)[/tex]; [tex]\( 6 \notin B \)[/tex]

C. [tex]\( 8 \in A \)[/tex]; [tex]\( 8 \in B \)[/tex]

D. [tex]\( 9 \in A \)[/tex]; [tex]\( 9 \in B \)[/tex]


Sagot :

Let's analyze the given sets [tex]\( A \)[/tex] and [tex]\( B \)[/tex] and determine the truth of each statement.

Firstly, define the sets based on the conditions provided:

- Set [tex]\( A = \{ x \mid x \in U \text{ and } x + 2 > 10 \} \)[/tex]

To find the condition for set [tex]\( A \)[/tex]:
[tex]\[ x + 2 > 10 \implies x > 8 \][/tex]
So, [tex]\( A = \{ x \mid x > 8 \} \)[/tex].

- Set [tex]\( B = \{ x \mid x \in U \text{ and } 2x > 10 \} \)[/tex]

To find the condition for set [tex]\( B \)[/tex]:
[tex]\[ 2x > 10 \implies x > 5 \][/tex]
So, [tex]\( B = \{ x \mid x > 5 \} \)[/tex].

Now, let's determine the truth of each pair of statements:

1. [tex]\( 5 \in A ; 5 \in B \)[/tex]

- Check if [tex]\( 5 \in A \)[/tex]:
[tex]\[ 5 + 2 > 10 \implies 7 > 10 \quad \text{(False)} \][/tex]
So, [tex]\( 5 \notin A \)[/tex].

- Check if [tex]\( 5 \in B \)[/tex]:
[tex]\[ 2 \cdot 5 > 10 \implies 10 > 10 \quad \text{(False)} \][/tex]
So, [tex]\( 5 \notin B \)[/tex].

Since both parts are false:
[tex]\[ \text{The statement } 5 \in A ; 5 \in B \text{ is False}. \][/tex]

2. [tex]\( 6 \in A ; 6 \notin B \)[/tex]

- Check if [tex]\( 6 \in A \)[/tex]:
[tex]\[ 6 + 2 > 10 \implies 8 > 10 \quad \text{(False)} \][/tex]
So, [tex]\( 6 \notin A \)[/tex].

- Check if [tex]\( 6 \in B \)[/tex]:
[tex]\[ 2 \cdot 6 > 10 \implies 12 > 10 \quad \text{(True)} \][/tex]
So, [tex]\( 6 \in B \)[/tex].

Since the first part is false and the second part contradicts by being true:
[tex]\[ \text{The statement } 6 \in A ; 6 \notin B \text{ is False}. \][/tex]

3. [tex]\( 8 \in A ; 8 \in B \)[/tex]

- Check if [tex]\( 8 \in A \)[/tex]:
[tex]\[ 8 + 2 > 10 \implies 10 > 10 \quad \text{(False)} \][/tex]
So, [tex]\( 8 \notin A \)[/tex].

- Check if [tex]\( 8 \in B \)[/tex]:
[tex]\[ 2 \cdot 8 > 10 \implies 16 > 10 \quad \text{(True)} \][/tex]
So, [tex]\( 8 \in B \)[/tex].


Since the first part is false:
[tex]\[ \text{The statement } 8 \in A ; 8 \in B \text{ is False}. \][/tex]

4. [tex]\( 9 \in A ; 9 \in B \)[/tex]

- Check if [tex]\( 9 \in A \)[/tex]:
[tex]\[ 9 + 2 > 10 \implies 11 > 10 \quad \text{(True)} \][/tex]
So, [tex]\( 9 \in A \)[/tex].

- Check if [tex]\( 9 \in B \)[/tex]:
[tex]\[ 2 \cdot 9 > 10 \implies 18 > 10 \quad \text{(True)} \][/tex]
So, [tex]\( 9 \in B \)[/tex].

Since both parts are true:
[tex]\[ \text{The statement } 9 \in A ; 9 \in B \text{ is True}. \][/tex]

So, the correct analysis leads to the conclusion that the correct pair of statements is:
[tex]\[ 9 \in A ; 9 \in B \][/tex]

The final answer is:
[tex]\[ (False, False, False, True) \][/tex]