Question

which figure correctly demonstrates using a straight line to determine that the graphed equation is not a function of x?

Explanation:

Step1: Recall vertical line test rule

A graph is a function of $x$ if no vertical line intersects it more than once. To show it’s not a function, a vertical line must intersect the graph twice.

Step2: Analyze the circle graph

The top graph is a circle. The vertical line drawn intersects the circle at two points, violating the vertical line test.

Answer:

The top figure (circle with intersecting vertical line)