Which of the following sets represents a function?
2 answers:
A function is a special relationship where each input has a single output.
A. The set {(3, 5), (-1, 7), (3, 9)} doesn't represent a function, because input x=3 has two outputs and
C. The set {(1, 2), (1, 4), (1, 6)} doesn't represent a function, because input x=1 has three outputs
and
B. The set {(1, 2), (3, 2), (5, 7)} represents a function, because each input has a single output.
Answer: correct choice is B.
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Answer: 
Note: to write the domain in interval notation, you'd write [-4,5]
if you need the domain in set-builder notation, then you'd write
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Explanation:
The domain is the set of possible x input values. Look at the left most point (-4,-1). The x coordinate here is x = -4. This is the smallest x value allowed. The largest x value allowed is x = 5 for similar reasons, but on the other side of the graph.
So that's how I got (x is between -4 and 5; inclusive of both endpoints)
Writing [-4,5] for interval notation tells us that we have an interval from -4 to 5 and we include both endpoints. The square brackets mean "include endpoint"
Writing is the set-builder notation way of expressing the domain. The 
portion means "x is a real number"
Note: to write the domain in interval notation, you'd write [-4,5]
if you need the domain in set-builder notation, then you'd write
------------------------------------------------------------------------------
Explanation:
The domain is the set of possible x input values. Look at the left most point (-4,-1). The x coordinate here is x = -4. This is the smallest x value allowed. The largest x value allowed is x = 5 for similar reasons, but on the other side of the graph.
So that's how I got
Writing [-4,5] for interval notation tells us that we have an interval from -4 to 5 and we include both endpoints. The square brackets mean "include endpoint"
Writing