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§ 2.1

§ 2.1. Introduction to Functions. Relation p 96. Definition of a Relation A relation is any set of ordered pairs. The set of all first components of the ordered pairs is called the domain of the relation

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§ 2.1

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  1. §2.1 Introduction to Functions

  2. Relation p 96 Definition of a Relation A relation is any set of ordered pairs. The set of all first components of the ordered pairs is called the domain of the relation and the set of all second components is called the range of the relation. Blitzer, Intermediate Algebra, 5e – Slide #2 Section 2.1

  3. Relation p 96 Check Point 1Find the domain and the range of the relation: {(0, 9.1), (10, 6.7), (20, 10.7), (30, 13.2), (34, 15.5)} Domain: {0, 10, 20, 30, 34} Range: {9.1, 6.7, 10.7, 13.2, 15.5} What is the rule that assigned the “inputs” in the domain to the “outputs” in the range? For example, for the ordered pair (30, 13.2), how does the data in Figure 2.1(a), which shows the percentage of first-year US college students claiming no religious affiliation. 9.1 0 10 6.7 10.7 20 13.2 30 15.5 34 Domain Range Blitzer, Intermediate Algebra, 5e – Slide #3 Section 2.1

  4. Functions p 98 Definition of a Function A function is a correspondence from a first set, called the domain, to a second set, called the range, such that each element in the domain corresponds to exactly one element in the range. (Each x corresponds to exactly one y in a function. Values of x have to be “faithful” – so to speak – that is, each x goes to exactly one y. However, a y value may be the image of more than one x – so y’s are not required to be “faithful”) For example, the following relation is a function: {(1,2), (2,3), (3,5), (4,3)} Note that the y value 3 is the image of two x values. Blitzer, Intermediate Algebra, 5e – Slide #4 Section 2.1

  5. Basic Functions 98 EXAMPLE Determine whether the following is a function. 1 drums guitar 2 violin 3 flute 4 Domain Range SOLUTION Yes, because none of the members of the domain correspond to more than one member of the range. Blitzer, Intermediate Algebra, 5e – Slide #5 Section 2.1

  6. Basic Functions 98 EXAMPLE Determine whether the following is a function. 3 ants beetles 8 crickets 5 moths 9 Domain Range SOLUTION No, because one of the members of the domain, 9, corresponds to more than one member of the range. Blitzer, Intermediate Algebra, 5e – Slide #6 Section 2.1

  7. Functions 99 • Example: Determine whether each relation is a function: • (a) {(2,3), (4,5), (6,5), (9,10)} • Yes – a function • (b) {(1,2), (3,3), (6,8), (1,10)} • (b) No – not a function since 1 is mapped to 2 and 10 • (c) {(1,5), (4,5), (2,5), (3,5)} • (c) Yes – a function Blitzer, Intermediate Algebra, 5e – Slide #7 Section 2.1

  8. Relation p 99 Check Point 2Determine whether each relation is a function: a. {(1,2), (3, 4), (5, 6), (5, 7)} Not a function b. {(1, 2), (3, 4), (6, 5), (7, 5)} function Blitzer, Intermediate Algebra, 5e – Slide #8 Section 2.1

  9. Functions as Equations 99 Functions are usually given in terms of equations rather than as sets of ordered pairs. For example, consider the function y = 2x – 3 For each value of x, there is one and only one value of y. The variable x is called the independent variable and the variable y is called the dependent variable. Blitzer, Intermediate Algebra, 5e – Slide #9 Section 2.1

  10. Function Notation 100 If an equation in x and y gives only one value of y for each value of x, then the variable y is a function of the variable x. When an equation represents a function, the function is often named by a letter such as f, g, h, F, G, or H. The output value, the y value, is often denoted by f(x), read “f of x” or “f at x” The notation f(x) does not mean “f times x”. The notation describes the value of the function f at x. Blitzer, Intermediate Algebra, 5e – Slide #10 Section 2.1

  11. Basic Functions 100 EXAMPLE Find the indicated function value: SOLUTION Replace x with 3 Evaluate the exponent Multiply Add and Subtract Blitzer, Intermediate Algebra, 5e – Slide #11 Section 2.1

  12. Basic Functions 101 EXAMPLE Find the indicated function value: SOLUTION Replace z with -4 Evaluate the exponents Multiply Add Blitzer, Intermediate Algebra, 5e – Slide #12 Section 2.1

  13. Basic Functions 101 Check Point 3a. Find the indicated function value: SOLUTION Replace x with 6 Multiply Add and Subtract Blitzer, Intermediate Algebra, 5e – Slide #13 Section 2.1

  14. Basic Functions 100 Check Point 3b. Find the indicated function value: SOLUTION Replace x with -5 Evaluate the exponent Multiply Add and Subtract Blitzer, Intermediate Algebra, 5e – Slide #14 Section 2.1

  15. Basic Functions 100 Check Point 3c. Find the indicated function value: SOLUTION Replace r with -4 Evaluate the exponent Multiply Add and Subtract Blitzer, Intermediate Algebra, 5e – Slide #15 Section 2.1

  16. Basic Functions 101 EXAMPLE Find the indicated function value: SOLUTION Replace w with x+y Rewrite exponent Multiply Add Distribute NOTE: THIS CANNOT BE SIMPLIFIED ANY FURTHER!!! Blitzer, Intermediate Algebra, 5e – Slide #16 Section 2.1

  17. Basic Functions 101 Check Point 3d. Find the indicated function value: SOLUTION Replace x with a+h Multiply NOTE: THIS CANNOT BE SIMPLIFIED ANY FURTHER!!! Blitzer, Intermediate Algebra, 5e – Slide #17 Section 2.1

  18. DONE

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