Writing a Function RuleUnit #3

Lesson 8

x f(x)1 22 33 44 5

Ask yourself: “What must I do to turn 1 into 2, 2 into 3, 3 into 4, and so on?”

A rule for the function is f(x) = x + 1.

Add 1 to the x value to get the y value.

Writing a Function Rule

https://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-368404-0/data/media/Ch05/academy123_content/wl-book-demo/ph-077.html

Writing a Function From a Table

Write a function rule for each table.

x ƒ(x)–1 –4 0 –3 1 –2 2 –1

b.x y–1 –5 0 0 1 5 2 10

a.

y = 5x ƒ(x) = x – 3

Examples:

Practice:

http://www.phschool.com/webcodes10/index.cfm?wcprefix=ate&wcsuffix=0504&area=view&x=-853&y=-349

Writing a Function From Words

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

Relate:    is  25  times  money earned

number of ads sold

Write: = 25 • nf(n)

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

Relate: is $5.50 times minus cost of tape production

total profit tapes sold

Write: = 5.5 • – 100xf(x)

Writing a Function Rule

1.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

2.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.

T(c) = 0.82c

s(m) = 6m

P(n) = 1.5n - 60

Examples: