1. 5-4 Notes: Writing a Function Rule

2. Example 1: Writing a Function Rule from a Table
What do you do to x to get f(x)? X
f(X) 1 5 2 6 3 7 4 8
Relate: f(x) equals x plus 4
f(x)= x + 4

3. 2. x y 1 3 9 6 36 81
Relate: y equals x times itself
y = x2

4. 3. x
f(x) 1 -1 2 3 4
Relate: f(x) equals x minus 2
f(x)= x-2

5. 4. x y 1 2 4 3 6 8
Relate: y equals x times 2
y = 2x

6. 5. x y 1 3 2 4 5 6
Relate: y equals x plus 2
y = x + 2

7. Example 2: Real World Problem Solving
A carpenter buys finishing nails by the pound. Each pound of nails costs $1.19. Write a function rule to describe this relationship.
Relate: cost equals 1.19 times nails (x)
C(x) = 1.19x

8. C(12)=1.19 (12) $14.28 How much do 12lb of finishing nails cost?
2. From problem 1. c(x)= 1.19x:
How much do 12lb of finishing nails cost?
C(12)=1.19 (12)
$14.28

9. Relate: profit is $18 times lawns mowed minus cost of mower.
3. Suppose you borrow money from a relative to buy a lawn mower that costs $245. You charge $18 to mow a lawn. Write a rule to describe your profit as a function of the number of lawns mowed.
Relate: profit is $18 times lawns mowed minus cost of mower.
Define: let n=number of lawns mowed & p=profit p(n)=18n-245

10. Define: let h=number of hours & p=total profit p(h)=15h-199
4. Suppose you buy a word-processing software package that costs $199. You charge $15 per hour for word processing. Write a function rule to describe your profit as a function of the number of hours you work.
Relate: total profit is $15 times number of hour of word processing minus cost of word processor.
Define: let h=number of hours & p=total profit p(h)=15h-199

11. HW # 14 Page 256 (1-18)