Question

select all of the following graphs which represent y as a function of x.

Explanation:

Step1: Recall vertical - line test

A graph represents $y$ as a function of $x$ if and only if any vertical line drawn on the graph intersects the graph at most once.

Step2: Analyze the first graph

The first graph is a straight - line. For any vertical line drawn on this straight - line graph, it will intersect the line at exactly one point. So, it represents $y$ as a function of $x$.

Step3: Analyze the second graph (circle)

For a circle, a vertical line can intersect the circle at two points. For example, for a standard - form circle $(x - a)^2+(y - b)^2=r^2$, when we consider vertical lines $x = a\pm r$, they will intersect the circle at two points. So, it does not represent $y$ as a function of $x$.

Answer:

The first graph represents $y$ as a function of $x$. The second graph (circle) does not represent $y$ as a function of $x$.