<< Chapter < Page Chapter >> Page >

Restricting the domain

If a function is not one-to-one, it cannot have an inverse. If we restrict the domain of the function so that it becomes one-to-one, thus creating a new function, this new function will have an inverse.

Given a polynomial function, restrict the domain of a function that is not one-to-one and then find the inverse.

  1. Restrict the domain by determining a domain on which the original function is one-to-one.
  2. Replace f ( x ) with y .
  3. Interchange x and y .
  4. Solve for y , and rename the function or pair of function f −1 ( x ) .
  5. Revise the formula for f −1 ( x ) by ensuring that the outputs of the inverse function correspond to the restricted domain of the original function.

Restricting the domain to find the inverse of a polynomial function

Find the inverse function of f :

  1. f ( x ) = ( x 4 ) 2 ,   x 4
  2. f ( x ) = ( x 4 ) 2 ,   x 4

The original function f ( x ) = ( x 4 ) 2 is not one-to-one, but the function is restricted to a domain of x 4 or x 4 on which it is one-to-one. See [link] .

Two graphs of f(x)=(x-4)^2 where the first is when x>=4 and the second is when x<=4.

To find the inverse, start by replacing f ( x ) with the simple variable y .

y = ( x 4 ) 2 Interchange x and  y . x = ( y 4 ) 2 Take the square root . ± x = y 4 Add   4   to both sides . 4 ± x = y

This is not a function as written. We need to examine the restrictions on the domain of the original function to determine the inverse. Since we reversed the roles of x and y for the original f ( x ) , we looked at the domain: the values x could assume. When we reversed the roles of x and y , this gave us the values y could assume. For this function, x 4 , so for the inverse, we should have y 4 , which is what our inverse function gives.

  1. The domain of the original function was restricted to x 4 , so the outputs of the inverse need to be the same, f ( x ) 4 , and we must use the + case:
    f 1 ( x ) = 4 + x
  2. The domain of the original function was restricted to x 4 , so the outputs of the inverse need to be the same, f ( x ) 4 , and we must use the – case:
    f 1 ( x ) = 4 x
Got questions? Get instant answers now!
Got questions? Get instant answers now!

Finding the inverse of a quadratic function when the restriction is not specified

Restrict the domain and then find the inverse of

f ( x ) = ( x 2 ) 2 3.

We can see this is a parabola with vertex at ( 2 , –3 ) that opens upward. Because the graph will be decreasing on one side of the vertex and increasing on the other side, we can restrict this function to a domain on which it will be one-to-one by limiting the domain to x 2.

To find the inverse, we will use the vertex form of the quadratic. We start by replacing f ( x ) with a simple variable, y , then solve for x .

y = ( x 2 ) 2 3    Interchange  x  and  y . x = ( y 2 ) 2 3    Add 3 to both sides . x + 3 = ( y 2 ) 2    Take the square root . ± x + 3 = y 2    Add 2 to both sides . 2 ± x + 3 = y    Rename the function . f 1 ( x ) = 2 ± x + 3

Now we need to determine which case to use. Because we restricted our original function to a domain of x 2 , the outputs of the inverse should be the same, telling us to utilize the + case

f 1 ( x ) = 2 + x + 3

If the quadratic had not been given in vertex form, rewriting it into vertex form would be the first step. This way we may easily observe the coordinates of the vertex to help us restrict the domain.

Got questions? Get instant answers now!
Got questions? Get instant answers now!

Find the inverse of the function f ( x ) = x 2 + 1 , on the domain x 0.

f 1 ( x ) = x 1

Got questions? Get instant answers now!

Questions & Answers

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 1

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Algebra and trigonometry' conversation and receive update notifications?

Ask