1 6 Relations and Functions Warm Up Lesson

1 -6 Relations and Functions Warm Up Lesson Presentation Lesson Quiz Holt Algebra 22

1 -6 Relations and Functions Warm Up Use the graph for Problems 1– 2. 1. List the x-coordinates of the points. – 2, 0, 3, 5 2. List the y-coordinates of the points. 3, 4, 1, 0 Holt Algebra 2

1 -6 Relations and Functions Objectives Identify the domain and range of relations and functions. Determine whether a relation is a function. Holt Algebra 2

1 -6 Relations and Functions Vocabulary relation domain range function Holt Algebra 2

1 -6 Relations and Functions A relation is a pairing of input values with output values. It can be shown as a set of ordered pairs (x, y), where x is an input and y is an output. The set of input values for a relation is called the domain, and the set of output values is called the range. Holt Algebra 2

1 -6 Relations and Functions Mapping Diagram Domain Range A 2 B C Set of Ordered Pairs {(2, A), (2, B), (2, C)} (x, y) Holt Algebra 2 (input, output) (domain, range)

1 -6 Relations and Functions Example 1: Identifying Domain and Range Give the domain and range for this relation: {(100, 5), (120, 5), (140, 6), (160, 6), (180, 12)}. List the set of ordered pairs: {(100, 5), (120, 5), (140, 6), (160, 6), (180, 12)} Domain: {100, 120, 140, 160, 180} The set of x-coordinates. Range: {5, 6, 12} Holt Algebra 2 The set of y-coordinates.

1 -6 Relations and Functions Check It Out! Example 1 Give the domain and range for the relation shown in the graph. List the set of ordered pairs: {(– 2, 2), (– 1, 1), (0, 0), (1, – 1), (2, – 2), (3, – 3)} Domain: {– 2, – 1, 0, 1, 2, 3} The set of x-coordinates. Range: {– 3, – 2, – 1, 0, 1, 2} Holt Algebra 2 The set of y-coordinates.

1 -6 Relations and Functions Suppose you are told that a person entered a word into a text message using the numbers 6, 2, 8, and 4 on a cell phone. It would be difficult to determine the word without seeing it because each number can be used to enter three different letters. Holt Algebra 2

1 -6 Relations and Functions Number {Number, Letter} {(6, M), (6, N), (6, O)} {(2, A), (2, B), (2, C)} {(8, T), (8, U), (8, V)} {(4, G), (4, H), (4, I)} Holt Algebra 2 The numbers 6, 2, 8, and 4 each appear as the first coordinate of three different ordered pairs.

1 -6 Relations and Functions A relation in which the first coordinate is never repeated is called a function. In a function, there is only one output for each input, so each element of the domain is mapped to exactly one element in the range. Holt Algebra 2

1 -6 Relations and Functions Although a single input in a function cannot be mapped to more than one output, two or more different inputs can be mapped to the same output. Holt Algebra 2

1 -6 Relations and Functions Not a function: The relationship from number to letter is not a function because the domain value 2 is mapped to the range values A, B, and C. Function: The relationship from letter to number is a function because each letter in the domain is mapped to only one number in the range. Holt Algebra 2

1 -6 Relations and Functions Example 2: Determining Whether a Relation is a Function Determine whether each relation is a function. A. from the items in a store to their prices on a certain date There is only one price for each different item on a certain date. The relation from items to price makes it a function. B. from types of fruits to their colors A fruit, such as an apple, from the domain would be associated with more than one color, such as red and green. The relation from types of fruits to their colors is not a function. Holt Algebra 2

1 -6 Relations and Functions Check It Out! Example 2 Determine whether each relation is a function. A. Holt Algebra 2 There is only one price for each shoe size. The relation from shoe sizes to price makes is a function.

1 -6 Relations and Functions Every point on a vertical line has the same x-coordinate, so a vertical line cannot represent a function. If a vertical line passes through more than one point on the graph of a relation, the relation must have more than one point with the same xcoordinate. Therefore the relation is not a function. Holt Algebra 2

1 -6 Relations and Functions Holt Algebra 2

1 -6 Relations and Functions Example 3 A: Using the Vertical-Line Test Use the vertical-line test to determine whether the relation is a function. If not, identify two points a vertical line would pass through. This is a function. Any vertical line would pass through only one point on the graph. Holt Algebra 2

1 -6 Relations and Functions Example 3 B: Using the Vertical-Line Test Use the vertical-line test to determine whether the relation is a function. If not, identify two points a vertical line would pass through. This is not a function. A vertical line at x = 1 would pass through (1, 1) and (1, – 2). Holt Algebra 2

1 -6 Relations and Functions Check It Out! Example 3 a Use the vertical-line test to determine whether the relation is a function. If not, identify two points a vertical line would pass through. This is a function. Any vertical line would pass through only one point on the graph. Holt Algebra 2

1 -6 Relations and Functions Check It Out! Example 3 a Use the vertical-line test to determine whether the relation is a function. If not, identify two points a vertical line would pass through. This is not a function. A vertical line at x = 1 would pass through (1, 2) and (1, – 2). Holt Algebra 2

1 -6 Relations and Functions Lesson Quiz: Part I 1. Give the domain and range for this relation: {(10, 5), (20, 5), (30, 5), (60, 100), (90, 100)}. D: {10, 20, 30, 60, 90)} R: {5, 100} Determine whether each relation is a function. 2. from each person in class to the number of pets he or she has function 3. from city to zip code Holt Algebra 2 not a function

1 -6 Relations and Functions Lesson Quiz: Part II Use the vertical-line test to determine whether the relation is a function. If not, identify two points a vertical line would pass through. 4. not a function; possible answer: (3, 2) and (3, – 2) Holt Algebra 2