Respuesta :

The graph of a curve that passes the vertical line test is known as a function. Functions are graphical representations that may have multiple x-values for a given y-coordinate, but will never have multiple y-values for any given x-coordinate.
Hope that helped! =)
it is called function.  to use the vertical line test, take a ruler or other straight edge and draw a line parallel to the y-axis for any chosen value of x. If the 
vertical line you drew intersects the graph more than once for any value of x then the graph is not the graph of a function.