Section 3.6 Functions 265 The set of pairs is called a relation. The first piece of information is the input value, or x-value. The second piece of information is the output value, or y-value. The set of all x-coordinates of a relation is called the domain and the set of all y-coordinates of a relation is called the range. ������������������������ A relation is a set of ordered pairs in which the first coordinate of the ordered pairs comes from a set called the domain and the second coordinate of the ordered pairs comes from a set called the range. Relations can be expressed in various forms: a graph, a table, a mapping, a set of ordered pairs, or an equation. Some examples are shown. Graph Table Mapping x y 0 15,000 1 12,500 2 10,000 3 7500 4 5000 5 2500 6 0 6 –4 –2 x Set of ordered pairs Equation {(1, 3), (2, 4), (3, 5), (4, 6)} y = 0.24x + 4.42 Student Credit Hours Aisha Juan Hussein Rose When we state the domain or range of a relation, it is not necessary to list values more than once. �� ������������������������ ������������������ Express each described relation in the requested form. State the domain and range of each relation. 1a. A class was surveyed to determine which students were enrolled in a specific number of hours. The results are shown in the following mapping. Write this relation as a set of ordered pairs. 6 12 15 18 Todd Amari Rosa Julia Sean Aretha Judith 1b. According to T-Mobile.com, each text message sent or received in the United States costs $0.20 if you do not have a messaging plan. Express the relation between the number of text messages sent or received and the cost associated with them as an equation. 1c. The network TV ad revenue (in millions) for the NCAA Division I Men’s Basketball Championship is given in the table. Express this relation in a graph. (Source: http://www.internetadsales.com/march-madness-advertising-trends-report) Year 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Revenue 319 318 358 380 451 475 500 520 643 589 (in millions) 3 6 12 15 2 2 4 4 –2 y
hendricks_beginning_algebra_1e_ch1_3
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