Graphing, Domain and Range of Functions Topic Index |
Algebra2/Trig Index | Regents Exam Prep Center  The domain is
the set of all first elements of ordered pairs (x-coordinates).
The range is the set of all second elements of ordered pairs
(y-coordinates).  Domain and range can be seen clearly from a
graph.  Example 1: Example 2:  Domain: {1, 3, 4, 6} Range:  {-2,
2, 5}  Domain: (all real numbers)   The two examples shown above
are functions.  But, as we know, not all graphs are functions. 
The graph at the left is:   Since the graph FAILS the Vertical
Line Test, this relation is not a function.  If we restrict the
graph to only the "positive" (or we could have chosen negative)
y-values, the graph will be a function:
   (graph below)   In a similar fashion, we can also restrict
domains to ensure that graphs are functions.  The graph at the
left is:    If the domain for this graph is listed as "all Real
numbers", this relation is NOT a function.  At first glance this
graph appears t