21-4: Patterns and Functions A function is a relationship that assigns exactly one output value for each input value. For each input value, there is only one corresponding output.A function rule, such as C = p p, is an equation that defines a functional relationship.
31-4: Patterns and Functions Example 1: Writing a Function RuleThe relationship between the number of loads of laundry and cost is given below. Use the table to write a function rule.Determine variable names to useLet n = number of loads Let c = costDetermine the difference between successive entries.$ $2.75 = $2.75 $ $5.50 = $11.00 – $8.25 = 2.75Work backwards to determine if there would have been any cost with 0 loads.Nopec = 2.75 • n
41-4: Patterns and Functions Your Turn: Writing a Function RuleThe relationship between the number of hours and the total miles driven is given below. Use the table to write a function rule.m = 60 • h
51-4: Patterns and Functions Example 2: Writing a Function Rule (with starting point)The relationship between the number of houses built and number of toothpicks used.Determine variable names to useLet h = number of housesLet t = number of toothpicksDetermine the difference between successive entries.11 – 6 = 5 16 – 11 = 5 21 – 16 = 5Work backwards to determine if there would have been any cost with 0 houses.6 – 5 = 1c = 5 • n + 1
61-4: Patterns and Functions Your Turn: Writing a Function Rule (with a starting point)The relationship between an input (x) and output (y) is given below. Determine the function for the data in the table.y = 3x + 2
71-4: Patterns and Functions The relationship between the number of houses built and number of toothpicks used.In this example, the number of toothpicks t depends on the number of houses h to be built.This makes t the dependent variable, and h the independent variable.In most real-world scenarios, the independent variable is the one you can control.
81-4: Patterns and Functions Example 3The cost of a memory stick is shown in the table below. Determine the dependent and independent variables.Because the cost DEPENDS on the amount of memory you wish to purchase, the cost is the dependent variableBecause you control how much memory you wish to buy, memory is the INDEPENDENT variable.
91-4: Patterns and Functions Your TurnDetermine the independent and dependent variable in the scenario below.The cooking time for an unstuffed turkey is about 20 minutes per pound.Dependent variable:Independent variable:The cooking timeThe number of pounds to cook
101-4: Patterns and Functions The possible values for input (or independent variable) of a function are the domain of the function. The possible values of the output (dependent variable) are the range of the function.Example 4: Reasonable domain and rangeMaria earns $7 an hour for babysitting after school and on Saturday. She works no more than 16 hours a week.Identify the independent and dependent quantitiesShe controls the number of hours she works, so that is the independent variable.The amount she earns is the dependent variable (her pay DEPENDS on the amount of hours she works)Find a reasonable domain and range for this situationShe works no more than 16 hours a week, so a reasonable domain is anything from 0 to 16 hours.A reasonable range is anything from $0 to $112 (7 • 16)
111-4: Patterns and Functions Your TurnCharlie downloads songs for $0.75 each. He has between $3.00 and $6.00 to spend on songs.Identify the independent and dependent variables.Independent variable: The amount of money he decides to spendDependent variable: How many songs he downloadsFind a reasonable domain and range.Domain: Anything from $3 to $6Range: Anything from 4 to 8 songs (3/0.75 and 6/0.75)
121-4: Patterns and Functions AssignmentPractice Worksheet 1-4All problemsTomorrowQuiz on Sections 1-1 through 1-3