Question 174846
Determine whether the relation {(3,2),(4,5),(-3,5),(-4,2)} is a function
<pre><font size = 4 color = "indigo"><b>
Yes it is a function because the four first 
coordinates 3,4,-3, and -4 are all different.

(Note: It doesn't matter that the second 
coordinates 2,5,5, and 2 are not all different. 
Only all the first coordinates must be different
in order for a relation to be a function)

The graph consists of these 4 points:

{{{drawing(400,400,-6,6,-6,6, grid(1), 
circle(3,2,.1),
circle(3,2,.05), 
circle(4,5,.1),
circle(4,5,.05), 
circle(-3,5,.1),
circle(-3,5,.05), 
circle(-4,2,.1),
circle(-4,2,.05), 
circle(3,2,.15),
circle(3,2,.125), 
circle(4,5,.15),
circle(4,5,.125), 
circle(-3,5,.15),
circle(-3,5,.125), 
circle(-4,2,.15),
circle(-4,2,.125) 


)}}} 

Notice that no point is directly above or
below any other point.  That is how you
can tell by looking at a graph whether
the relation is a function.  If any point
is directly above or below any other point,
then the relation is not a function.

Edwin</pre>