1. 2-1 Relations and Functions
The Domain of a relation is all the input numbers.
The Range of a relation is the output numbers.
A relation is a set of pairs of input and out put values. Relations can be wrote as a set of ordered pairs.
input
Graphing a relation
domain
Relation- (8,11),(4,9)
(8,11)
(6,7)
(4,9)
output
range
A function is a relation when each element of the domain is paired with exactly one element of the range.
Another way to show a relation is to use a mapping diagram. This links each domain with the corresponding range.
domain
range

2. Not a function
This is a function 5 1 2 3 4 5 1 6 6 2
This is not a function because the red line hits the blue line in three different places. 7 8 3 7
This is a function
The vertical-line test is to see whether a line passes through more then one point at a time. If it does pass over two or more points at a time then the relation is not a function.