Answer:
It is a function because it passes the vertical line test.
Step-by-step explanation:
A function is represented by a line or a curve on a coordinate plane where for each x-value, there is a unique y-value.
If you were to pass the edge of a ruler across a graph, parallel to the y-axis, and it crosses the graphed line or curve in more than one place, that line is not a function.
in the example shown here, a ruler would cross the red lines at only one point at a time. So this graph passes the vertical line test.
