Answer
$ a.\quad$ a function
$ b.\quad$
domain $=\mathbb{R}$
range $=\{y\in \mathbb{R}\ |\ y\geq 0\}$
Work Step by Step
$ a.\quad$
Apply the vertical line test:
If it is possible for a vertical line to cross a graph more than once,
then the graph is not the graph of a function.$7$
The graph passes the test, represents a function.
$ b.\quad$
The domain is the set of first coordinates of the points on the graph.
Here, domain $=\mathbb{R}$
The range is the set of second coordinates of the points on the graph.
Here, range $=\{y\in \mathbb{R}\ |\ y\geq 0\}$
