Writing a Function Rule

6. Writing a Function Rule Unit #6 Day 4

7. xy 1 2 2 3 3 4 4 5 Writing a Function Rule Ask yourself: “What must I do to turn 1 into 2, 2 into 3, 3 into 4, and so on?” Add 1 to the x value to get the y value. A rule for the function is y = x + 1.

8. Practice:

9. Writing a Function From Words • http://www.phschool.com/webcodes10/index.cfm?wcprefix=ate&wcsuffix=0504&area=view&x=-853&y=-349

10. money earned number of ads sold Relate:    is  25  times   f(n) n Write: = 25 • Writing a Function Rule The journalism class makes $25 per ad sold in the yearbook. If the class sells n ads, how much money will it earn? Write a function rule to describe this relationship. The function rule is f(n) = 25n

11. total profit tapes sold Relate: is $5.50 times minus cost of tape production f(x) Write: = 5.5 • – 100 x Writing a Function Rule The choir spent $100 producing audio tapes of its last performance and will sell the tapes for $5.50 each. Write a rule to describe the choir’s profit as a function of the number of tapes sold. The function rule is f(x) = 5.5x– 100

13. Homework • Page 272 • #1-8, 10-13, 17

14. x ƒ(x) –1 –4 0 –3 1 –2 2 –1 xy –1 –5 0 0 1 5 2 10 b. a. Writing a Function Rule 1. Write a function rule for each table. y = 5x ƒ(x) = x – 3 2. Write a function rule to describe each relationship. a. the total cost T(c) of c pounds of apples at $.82 a pound b. a scale model s of a moth m that is 6 times the actual size of the moth T(c) = 0.82c s(m) = 6m 3. You borrow $60 to buy a bread-making machine. You charge customers $1.50 a loaf for your special bread. Write a rule to describe your profit as a function of the number n of loaves sold. P(n) = 1.5n - 60