Operations on Functions
Take out last night’s homework & your notes! Put
your parent form in the hw box!
A functions domain is restricted over the real numbers iff…
1)
2)
State the domain of the function, using interval notation
! ! =!+3
! ! = !−8
! ! = 2! ! + 4! − 6
! ! =
!−5
2! + 4
! ! =!+
! ! = 9 − 3!
! ! =
2
! ! + 3!
1
!−1
Try the last part of your hw!
“Rainbow Method” (Split the Middle)
1) Multiply a*c
2) Bring down 1st and last term
3) Find 2 numbers which multiply to
be middle and add to be top
4) Split the middle term up!
5) Factor by grouping
Example:
8! ! − 10! − 3
A*C=______
6! ! + 19! + 10
6! ! + 13! − 8
8! ! + ___________ - _________ -3
2x( ________) -3(___________)
(___________) (___________)
Function Notation Quick Review:
! ! =!+7
Find:
!(_________) =
!(__________) =
Function Operations
(! + !) means….
(! − !) means…
! ∙ ! means…
!
!
means….
Function Composition
! ∘ ! ! = ____________________
Means…..
Find ________ first
Find ________ second
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!(__________) =
Graphically
(! ∘ !)(3)=
!∘! 1 =
Algebraically
! ! =
!
ℎ ! =
Numerically
! ! =
!
! ! =
Find (! ∘ ℎ)(!)
Find (! ∘ !)(4)
Group Task #1: Commission Conundrum
You work forty hours a week at a
furniture store. You receive a $220
weekly salary, plus a 3% commission on
sales over $5000. Assume that you sell
enough this week to get the commission.
Given the functions f (x) = 0.03x and g(x)
= x – 5000, which of (f o g)(x)and (g o f
)(x) represents your commission?
Explain why.
Group Task #2:
Macy’s is offering a huge selection of
designer shoes in its The Great Shoe
Sale promo. The store is advertising an
extra 30% off when you buy three (3) or
more pair of shoes, extra 20% off when
you buy two (2) pairs, or an extra 15%
off when you buy one (1) pair. As a loyal
customer, you have a star rewards pass
that entitles you with an additional $20
off for the purchase of any item that
costs $50 or more.
1. Using the information above, write a function f(x) that represents the price of a pair of
shoes after the $20 off rewards pass is applied. What is the domain of f(x)? Explain your
reasoning.
2. Write a function g(x) that represents the price of the same pair of shoe after the 15%
discount is applied. Show in detail how you arrived at your answer.
3. Compose functions f(x) and g(x) to represent the price of the pair of shoes when the $20
discount is applied first. Show in detail how you arrived at your answer.
4. Write the composite function that represents the price of the pair of shoes when the 15%
discount is applied first. What are the domain and range of this composite function?
Explain your reasoning.
5. Which order of discounts gives you a better deal? Justify your reasoning by evaluating
f(g(x)) and g(f(x)) at x= $120.
Homework:
Find (! + !)(!) and (! − !)(!) for each of the following functions:
1. ! ! = 7! − 5, ! ! = 3 − 2!
2. ! ! = −! − 4, ! ! = ! + 4
Find (!")(!) and
!
!
(!) for each of the following functions:
3. ! ! = ! + 2, ! ! = ! ! + 8! + 12
4. ! ! = ! ! − 9!, ! ! = ! + 3
5. Find ! ∘ ! ! and (! ∘ !)(!) for each of the following functions:
! ! = ! ! + 3, ! ! = 7! + 2
6. Suppose the graphs of f(x) and g(x) are both linear. Must it be true that the
graphs of (! ∘ !)(!) and (! ∘ !)(!) are also linear? Justify your answer.
7. Most functions are compositions of basic functions. Work backwards to
determine the basic functions that created the composition. (Think about an
“outside function” and an “inside function”).