Given that the universal set is all real numbers and set [tex]S[/tex] is defined as the set of all [tex]x[/tex] such that [tex]x[/tex] is less than 5, which of the following is the complement of [tex]S[/tex]?

[tex]S = \{x \mid x \ \textless \ 5\}[/tex]

A. [tex]\{x \mid x \neq 5\}[/tex]
B. [tex]\{6,7,8, \ldots\}[/tex]
C. [tex]\{x \mid x \ \textgreater \ 5\}[/tex]
D. [tex]\{x \mid x \geq 5\}[/tex]



Answer :

To determine the complement of the set [tex]\( S \)[/tex], we need to find all the elements in the universal set that are not in [tex]\( S \)[/tex]. Given that the universal set includes all real numbers and the set [tex]\( S \)[/tex] is defined as:
[tex]\[ S = \{x \mid x < 5\} \][/tex]

We are looking for the set of all [tex]\( x \)[/tex] that do not satisfy this condition.

Step-by-step solution to find the complement of [tex]\( S \)[/tex]:

1. Understand the definition of [tex]\( S \)[/tex]:
The set [tex]\( S \)[/tex] includes all real numbers less than 5. In other words, if [tex]\( x \)[/tex] is an element of [tex]\( S \)[/tex], then [tex]\( x < 5 \)[/tex].

2. Define the complement of [tex]\( S \)[/tex]:
The complement of [tex]\( S \)[/tex], denoted by [tex]\( S' \)[/tex], includes all real numbers that are not in [tex]\( S \)[/tex]. This means any real number [tex]\( x \)[/tex] that does not satisfy [tex]\( x < 5 \)[/tex].

3. Formulate the condition:
To find [tex]\( S' \)[/tex], we need to take all elements [tex]\( x \)[/tex] in the universal set of real numbers and exclude the elements that are in [tex]\( S \)[/tex]. This means all [tex]\( x \)[/tex] such that [tex]\( x \geq 5 \)[/tex].

Therefore, the complement of [tex]\( S \)[/tex] is given by:
[tex]\[ S' = \{x \mid x \geq 5\} \][/tex]

Review the options provided:
- [tex]\( \{x \mid x \neq 5\} \)[/tex]: This set includes all real numbers except 5. This is not the complement of [tex]\( S \)[/tex] since it includes numbers less than 5 and greater than 5, excluding only 5.
- [tex]\( \{6, 7, 8, \ldots\} \)[/tex]: This set includes only integers greater than 5 and not all real numbers greater than or equal to 5, so it's incorrect.
- [tex]\( \{x \mid x > 5\} \)[/tex]: This set includes all real numbers greater than 5 but excludes 5 itself. Therefore, this is not the correct complement set.
- [tex]\( \{x \mid x \geq 5\} \)[/tex]: This set includes all real numbers greater than or equal to 5, which correctly represents the complement of [tex]\( S \)[/tex].

The correct answer is:
[tex]\[ \{x \mid x \geq 5\} \][/tex]

Thus, we conclude that the complement of [tex]\( S \)[/tex] is:
[tex]\[ \{x \mid x \geq 5\} \][/tex]

In terms of the provided options, the correct one is the fourth option.