Theory of Sets
 A set is a welldefined collection of objects.
 Sets are usually represented by capital letters A, B, C, D, X, Y, Z, etc. The objects inside a set are called elements or members of a set. They are denoted by small letters a, b, c, d, x, y, z, etc.
 If a is an element of a set A, then we say that “a belongs to A” and mathematically we write it as “a∈A”; if b is not an element of A, then we write “b∉A”.
 There are three different ways of representing a set:
 Description method: Description about the set is made and it is enclosed in curly brackets { }.
For example, the set of composite numbers less than 30 is written as follows:
{Composite numbers less than 30}

 Roster method or tabular form: Elements are separated by commas and enclosed within the curly brackets { }.
For example, a set of all integers greater than 5 and less than 9 will be represented in roster form as {6, 7, 8}.

 Setbuilder form or rule method: All the elements of the set have a single common property that is exclusive to the elements of the set i.e., no other element outside the set has that pro…
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