1.10
MTH-4109-1 Sets, Relations and Functions
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g) G = {..., –3, –2, –1, 0, 1, 2, 3, ...}
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h) H = {0, 2, 4, ..., 94, 96, 98}
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3. Our typographer had a bad day and made a few mistakes listing the elements
of certain sets. Correct the errors.
a) A = {1 2 3 4 5} ...................................................................
b) B = {8, 8, 9, 10, 11, 11, 12} ...................................................................
c) c = {13, 14, 15, 16, 17, ...} ...................................................................
d) D = 1, 3, 5, 7, 9, 11 ...................................................................
We will know that a set is clearly defined if we can determine whether or not any
given element belongs to that set.
To indicate that any element belongs to a set, we use the symbol for
membership, which is denoted by ∈. For instance, the expression x ∈ C means
that element x is part of set C, that it is an element of set C or that it belongs to
set C.
We know that the element 4 belongs to the set of even natural numbers
P = {0, 2, 4, 6, 8, ...}. Hence, we can write 4 ∈ P.
To indicate that an element x belongs to a given set A, we
write x ∈ A.
x ∈ A means "x is an element of set A"
or
"x belongs to set A."