Answer:
1.) Element : A member of a set
2.) Null set : Set containing no elementa; also called the empty set.
3.) Set : A collection or group of objects indicated by braces, { }
4.) Subset : set A is a subset of set B if all of the elements of set A are contained in set B
Explanation:
Each individual member or value of any given set is called an element.
Consider:
Set A = {1.3, 5}
Each of 1, 3, 5 are the elements of A
Null set is an empty set denoted as {}
A set ; A defined above is called the Set A.
Subset =
Given the set B = {1, 3}
B is a subset of A ; since all elements of B are contained in A.
