Ed: The relationship is not a function because if I draw a horizontal line at y = 2, the horizonal line crosses the graph at two points.
Debra: The relationship is a function because it is a graph of two different
lines.
Alejandro: The relationship is not a function because x = 1 has two
different y-values.
Antoine: The relationship is a function because I can write an equation for
a line.
Which students are not correct and what is the flaw in their argument?