Domain
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Definition of Domain
Domain of a relation is the set of all xcoordinates of the ordered pairs of that relation.
Examples of Domain

Domain of the relation {(3,4), (9,8), (4,5)} is {3, 4, 9}.
Video Examples: How to Figure the Domain & Range of Ordered Pairs : Math Tips
Solved Example on Domain
Ques: Find the domain of f(x) = (x + 3)^{1}.
Choices:
A. ( ∞,  3) or ( 3,  ∞)B. ( 3, 3)
C. ( ∞,  3) or (3, ∞)
D. ( ∞, ∞)
Correct Answer: A
Solution:

Step 1:f(x) = (x + 3)^{1}.
Step 2:
Step 3: Domain of a function is the set of all possible input values for the function.
Step 4: Observe that the function is not defined only when x =  3.
Step 5: So, the domain for this function is ( ∞,  3) or ( 3,  ∞).
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