# 1.4 Homework: functions in the real world

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This module provides practice problems designed to mimic real life applications of functions.

Laura is selling doughnuts for 35¢ each. Each customer fills a box with however many doughnuts he wants, and then brings the box to Laura to pay for them. Let n represent the number of doughnuts in a box, and let $c$ represent the cost of the box (in cents).

• If the box has 3 doughnuts, how much does the box cost?
• If $c=\text{245}$ , how much does the box cost? How many doughnuts does it have?
• If a box has n doughnuts, how much does it cost?
• Write a function $c\left(n\right)$ that gives the cost of a box , as a function of the number of doughnuts in the box.

Worth is doing a scientific study of graffiti in the downstairs boy’s room. On the first day of school, there is no graffiti. On the second day, there are two drawings. On the third day, there are four drawings. He forgets to check on the fourth day, but on the fifth day, there are eight drawings. Let d represent the day, and g represent the number of graffiti marks that day.

• Fill in the following table, showing Worth’s four data points.  d (day) g (number of graffiti marks)
• If this pattern keeps up, how many graffiti marks will there be on day 10?
• If this pattern keeps up, on what day will there be 40 graffiti marks?
• Write a function $g\left(d\right)$ ) that gives the number of graffiti marks as a function of the day .

Each of the following is a set of points. Next to each one, write “yes” if that set of points could have been generated by a function, and “no” if it could not have been generated by a function. (You do not have to figure out what the function is. But you may want to try for fun—I didn’t just make up numbers randomly…)

• $\left(1,-1\right)\left(3,-3\right)\left(-1,-1\right)\left(-3,-3\right)$ ________
• $\left(1,\pi \right)\left(3,\pi \right)\left(9,\pi \right)\left(\pi ,\pi \right)$ ________
• $\left(1,1\right)\left(-1,1\right)\left(2,4\right)\left(-2,4\right)\left(3,9\right)\left(-3,9\right)$ ________
• $\left(1,1\right)\left(1,-1\right)\left(4,2\right)\left(4,-2\right)\left(9,3\right)\left(9,-3\right)$ ________
• $\left(1,1\right)\left(2,3\right)\left(3,6\right)\left(4,\text{10}\right)$ ________

$f\left(x\right)={x}^{2}+2x+1$

• $f\left(2\right)=$
• $f\left(-1\right)=$
• $f\left(\frac{3}{2}\right)=$
• $f\left(y\right)=$
• $f\left(\text{spaghetti}\right)=$
• $f\left(\sqrt{x}\right)$
• $f\left(f\left(x\right)\right)$

Make up a function that has something to do with movies .

• Think of a scenario where there are two numbers, one of which depends on the other. Describe the scenario, clearly identifying the independent variable and the dependent variable .
• Write the function that shows how the dependent variable depends on the independent variable.
• Now, plug in an example number to show how it works.

#### Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Advanced algebra ii: activities and homework. OpenStax CNX. Sep 15, 2009 Download for free at http://cnx.org/content/col10686/1.5
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