Answer: a) [tex]=\left \{ 5,\,9,\,27 \right \}[/tex]
(b) [tex]\left \{ x\ : X\varepsilon\mathbb{N} \right \text{and}\ x<2\}= \left \{1 \right \}[/tex]
(c) [tex]\left \{\epsilon \right \}[/tex]
(d) [tex]\left \{\right \}=\phi[/tex]
Explanation:
The formal description of the given sets are as follows :-
a) The set containing the numbers 5, 9, and 27.
[tex]=\left \{ 5,\,9,\,27 \right \}[/tex]
(b) The set that contains all the natural numbers less than 2.
[tex]\left \{ x\ : X\varepsilon\mathbb{N} \right \text{and}\ x<2\}= \left \{1 \right \}[/tex]
(c) The set containing the empty string.
We know that in formal description, the empty string is denoted with [tex]\epsilon[/tex].
Thus, the required set : [tex]\left \{\epsilon \right \}[/tex]
(d) The set containing nothing at all.
[tex]\left \{ \right \}=\phi[/tex]
