Writing {\displaystyle A=\{1,2,3,4\}}{\displaystyle A=\{1,2,3,4\}} means that the elements of the set A are the numbers 1, 2, 3 and 4. Sets of elements of A, for example {\displaystyle \{1,2\}}\{1, 2\}, are subsets of A.
Sets can themselves be elements. For example, consider the set {\displaystyle B=\{1,2,\{3,4\}\}}{\displaystyle B=\{1,2,\{3,4\}\}}. The elements of B are not 1, 2, 3, and 4. Rather, there are only three elements of B, namely the numbers 1 and 2, and the set {\displaystyle \{3,4\}}{\displaystyle \{3,4\}}.
The elements of a set can be anything. For example, {\displaystyle C=\{\mathrm {\color {red}red} ,\mathrm {\color {green}green} ,\mathrm {\color {blue}blue} \}}{\displaystyle C=\{\mathrm {\color {red}red} ,\mathrm {\color {green}green} ,\mathrm {\color {blue}blue} \}} is the set whose elements are the colors red, green and blue.
Answers & Comments
Answer:
This is a set
Step-by-step explanation:
Writing {\displaystyle A=\{1,2,3,4\}}{\displaystyle A=\{1,2,3,4\}} means that the elements of the set A are the numbers 1, 2, 3 and 4. Sets of elements of A, for example {\displaystyle \{1,2\}}\{1, 2\}, are subsets of A.
Sets can themselves be elements. For example, consider the set {\displaystyle B=\{1,2,\{3,4\}\}}{\displaystyle B=\{1,2,\{3,4\}\}}. The elements of B are not 1, 2, 3, and 4. Rather, there are only three elements of B, namely the numbers 1 and 2, and the set {\displaystyle \{3,4\}}{\displaystyle \{3,4\}}.
The elements of a set can be anything. For example, {\displaystyle C=\{\mathrm {\color {red}red} ,\mathrm {\color {green}green} ,\mathrm {\color {blue}blue} \}}{\displaystyle C=\{\mathrm {\color {red}red} ,\mathrm {\color {green}green} ,\mathrm {\color {blue}blue} \}} is the set whose elements are the colors red, green and blue.