Pairs of points
.
Plot the order of pairs
\_(1,3)_(1,0)_(2,-1).gif\")
The relation is 
The domain of the relation is the set of all first (x-coordinates) coordinates.
\The domain of the relation is: 
The range of the relation is the set of second (y-coordinates) coordinates.
\The range of the relation is 
Draw the vertical lines through the points. Observe that one vertical line
\passing through two points. This graph fails the vertical line test.
\_(1,3)_(1,0)_(2,-1)_vertical_line.gif\")
So, the relation is not a function.
No, the relation is not a function.