Answer:
It's not a function
Explanation:
A function it's like a "machine" that transform a value from a set to only one value from another set.
In mathematics: Let A and B sets, A is the domain and B is the codomain of the function f. f : A ⇒ B.
By the given above definition of a function, the graph shown indicates for example that f(0)= 1 and - 1; this contradicts the definition of the function.
So, the graph shown it's not a function