Definition of a Function: For every “x” value there is only one “y” value Given a Graph Given an Order Pair Domain and Range Method Method Method Use the Vertical Line Test Use the definition of a function Use the definition of a function Draw light vertical lines through the graph. If a line passes through more than one point on the graph at the same time, then it is not a function. Examine the domain (x-values) of the order pairs. If the same x-value appears with two different y-values, then it is not a function. 2, 3, 4, 0, 2, 1, 0, 5 This is not a function because the x-value (2), is paired to two different y-values (3 and -1) Examine the domain (x-values). If an x is pointing to two different y’s, then it is not a function. Domain Range –5 3 2 0 1 –4 –7 –2 This is not a function because the x value (1) is pointing to two different y’s (3 and – 2) The Academic Support Center at Daytona State College (Math 13 pg 1 of 1)

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# Definition of a Function: For every “x” value there is only one “y” value