The relation is a function
The domain of the relation is (-∞, ∞)
The range of a function is (-∞, 3]
How to determine if the relation is a function
The test conducted is the vertical line test
A vertical line is drawn on all the x-values, if the vertical line intersects the graph in more than one point, then the relation fails the vertical line test, and not a function.
The relation passed the vertical line test and it is considered a function.
The domain considers all the possible input values. The arrows at both extremes indicates that the domain is infinity at bo left and right.
The range is read to be all real numbers not more than 3