Final answer:
The equation x²+y²=100 does not represent y as a function of x because each x-value corresponds to two y-values, failing the vertical line test.
Step-by-step explanation:
The equation x²+y²=100 represents a circle with a radius of 10 centered at the origin on the coordinate plane. To determine if y is a function of x, we need to see if each x-value corresponds to exactly one y-value. For a circle, each x-value (except at the extremes of the diameter) corresponds to two y-values: one positive and one negative. Therefore, y is not a function of x because it does not pass the vertical line test—drawing a vertical line through the graph would intersect it in more than one point.