if a closed circle is ontop of an open circle..is it still a function?

Answer 1

No, if a closed circle (also known as a filled-in circle or solid dot) is on top of an open circle (also known as an empty or hollow dot), it means that the point is not well-defined. In the context of a graph, this indicates that there are multiple y-values for a single x-value, which violates the definition of a function. Hence, it is not a function.