Writing a Function Rule Section 4-5

Goals Goal To write equations that represent functions. Rubric Level 1 – Know the goals. Level 2 – Fully understand the goals. Level 3 – Use the goals to solve simple problems. Level 4 – Use the goals to solve more advanced problems. Level 5 – Adapts and applies the goals to different and more complex problems.

Vocabulary None

Writing a Function Rule An algebraic expression that defines a function is a function rule. The dependent variable is a function of the independent variable. y is a function of x.

Example: Writing a Function Rule Write a function rule that represents each sentence. A worker’s earnings e are a function of the number of hours n worked at a rate of $8.75 per hour. earnings are number of hours worked at a rate OF $8.75/hr. e = n 8.75 A function rule that represents this situation is: e = 8.75n

Your Turn: A helicopter hovers 40ft above the ground. Then, the helicopter climbs at a rate of 21ft/s. Write a rule that represents the helicopter’s height h above the ground as a function of time t. A function rule that represents this situation is: h = 21t + 40 height is 40ft increased by 21ft per secondh = t

Identify the independent and dependent variables. Write a function rule for the situation. A math tutor charges $35 per hour. The function for the amount a math tutor charges is C = 35h. The amount a math tutor charges depends on number of hours. Dependent: charges Independent: hours Let C represent the charges. Let h represent the number of hours of tutoring. Example: Writing Functions

A fitness center charges a $100 initiation fee plus $40 per month. The function for the amount the fitness center charges is C = 40m Identify the independent and dependent variables. Write a function rule for the situation. The total cost depends on the number of months, plus $100. Dependent: total cost Independent: number of months Let C represent the total cost. Let m represent the number of months Example: Writing Functions

Identify the independent and dependent variables. Write a function rule for the situation. Steven buys lettuce that costs $1.69/lb. The function for cost of the lettuce is C = 1.69x. The total cost depends on how many pounds of lettuce that Steven buys. Dependent: total cost Independent: pounds Let C represent the total cost. Let x represent the number of pounds Steven bought. Your Turn:

Identify the independent and dependent variables. Write a function rule for the situation. An amusement park charges a $6.00 parking fee plus $29.99 per person. The function for the total park cost is C = 29.99x + 6. The total cost depends on the number of persons in the car, plus $6. Dependent: total cost Independent: number of persons in the car Let C represent the total cost. Let x represent the number of persons in the car. Your Turn:

Joke Time What happened to the man who lost the whole left side of his body? He is all right now. What do you find in an empty nose? Finger prints. What did one eye say to the other eye? Between you and me something smells.

Assignment 4-5 Exercises Pg. 283 – 285: #8 – 50 even