• The domain
of a function is the set of x values for your function, if your
x values are the input.
The example that we'll use is the function y=20+1x.
• There are two types of domains
you can use, practical and theoretical.
The practical domain deals with numbers that are realistic in
a problem situation. For example, if the function y=20+x represented
a problem where y is the total pay for a babysitting job, the
20 represents $20 for just showing up, and the 1 means $1 per
house for x number of hours. Now the practical domain would be
between 0 and 10 hours, because that was the agreed job length.
type of domain.
a set of logical
be all real
of a function
is the set
of y values
for your function,
if y is the
• There are
two types of range as well, practical and theoretical. The
practical range for this function would be your pay for the 10
hours, which would be anywhere from $20 to $30.
The theoretical range again applies only to the function and
would be all real numbers.
• Some of these equations have
limits on both domain and range. For example, in the function
the theoretical domain is all real numbers, but the range would
be limited to all real numbers greater than or equal to negative
2. Other restrictions are specific to the functions, and most
easily seen in the graph.