Functions: Domain and Range
(page 2 of 2)
Sections:
Functions versus relations
, Domain and range
Let's return to the subject of domain and range. When functions are first introduced, you will probably
have some slightly pathetic "functions" and relations to deal with, being just sets of points. These won't be
terribly useful or interesting functions and relations, but your text wants you to get the idea of what the
domain and range are. For instance:
•
State the domain and range of the following relation. Is the relation a function?
{(2, –3), (4, 6), (3, –1), (6, 6), (2, 3)}
This list of points, being a relationship between certain
x
's and certain
y
's, is a relation. The
domain is all the
x
-values, and the range is all the
y
-values. You list the values without
duplication:
domain:
{2, 3, 4, 6}
range:
{–3, –1, 3, 6}
(It is customary to list these values in numerical order, but it is
not
required. Sets are called
"unordered lists", so you can list the numbers in any order you feel like. Just don't duplicate:
technically, repititions are okay in sets, but most instructions would count off for this.)
While this is a relation (because
x
's and
y
's are being related to each other), you have two points