Question

Which graph represents y as a function of x?

Answer 1

Answer:

Bottom left.

Step-by-step explanation:

In order for any of them to be the graph of a function you would need that given a value of x, you get no more than one value of y. Zero is fine, you just picked an x out of the domain.

In layman's terms it means that if you grab a ruler, a piece of paper, a pen, and you scan the graph moving the edge parallel to the y axis (ie, vertically) you are allowed to touch the graph only once. Top right is out. Bottom left is ok, bottom right is not: you have infinite points of contact in there.

Top left would be fine, if it wasn't for x = 1. In there you have two values marked with a solid dot. That makes it not the graph of a function.