<< Chapter < Page Chapter >> Page >

Does a linear, exponential, or logarithmic model best fit the data in [link] ? Find the model.

x 1 2 3 4 5 6 7 8 9
y 3.297 5.437 8.963 14.778 24.365 40.172 66.231 109.196 180.034

Exponential. y = 2 e 0.5 x .

Expressing an exponential model in base e

While powers and logarithms of any base can be used in modeling, the two most common bases are 10 and e . In science and mathematics, the base e is often preferred. We can use laws of exponents and laws of logarithms to change any base to base e .

Given a model with the form y = a b x , change it to the form y = A 0 e k x .

  1. Rewrite y = a b x as y = a e ln ( b x ) .
  2. Use the power rule of logarithms to rewrite y as y = a e x ln ( b ) = a e ln ( b ) x .
  3. Note that a = A 0 and k = ln ( b ) in the equation y = A 0 e k x .

Changing to base e

Change the function y = 2.5 ( 3.1 ) x so that this same function is written in the form y = A 0 e k x .

The formula is derived as follows

y = 2.5 ( 3.1 ) x = 2.5 e ln ( 3.1 x ) Insert exponential and its inverse . = 2.5 e x ln 3.1 Laws of logs . = 2.5 e ( ln 3.1 ) x Commutative law of multiplication

Change the function y = 3 ( 0.5 ) x to one having e as the base.

y = 3 e ( ln 0.5 ) x

Key equations

Half-life formula If   A = A 0 e k t , k < 0 , the half-life is   t = ln ( 2 ) k .
Carbon-14 dating t = ln ( A A 0 ) 0.000121 .
A 0   A   is the amount of carbon-14 when the plant or animal died
t   is the amount of carbon-14 remaining today
is the age of the fossil in years
Doubling time formula If   A = A 0 e k t , k > 0 , the doubling time is   t = ln 2 k
Newton’s Law of Cooling T ( t ) = A e k t + T s , where   T s   is the ambient temperature,   A = T ( 0 ) T s , and   k   is the continuous rate of cooling.

Key concepts

  • The basic exponential function is f ( x ) = a b x . If b > 1 , we have exponential growth; if 0 < b < 1 , we have exponential decay.
  • We can also write this formula in terms of continuous growth as A = A 0 e k x , where A 0 is the starting value. If A 0 is positive, then we have exponential growth when k > 0 and exponential decay when k < 0. See [link] .
  • In general, we solve problems involving exponential growth or decay in two steps. First, we set up a model and use the model to find the parameters. Then we use the formula with these parameters to predict growth and decay. See [link] .
  • We can find the age, t , of an organic artifact by measuring the amount, k , of carbon-14 remaining in the artifact and using the formula t = ln ( k ) 0.000121 to solve for t . See [link] .
  • Given a substance’s doubling time or half-time, we can find a function that represents its exponential growth or decay. See [link] .
  • We can use Newton’s Law of Cooling to find how long it will take for a cooling object to reach a desired temperature, or to find what temperature an object will be after a given time. See [link] .
  • We can use logistic growth functions to model real-world situations where the rate of growth changes over time, such as population growth, spread of disease, and spread of rumors. See [link] .
  • We can use real-world data gathered over time to observe trends. Knowledge of linear, exponential, logarithmic, and logistic graphs help us to develop models that best fit our data. See [link] .
  • Any exponential function with the form y = a b x can be rewritten as an equivalent exponential function with the form y = A 0 e k x where k = ln b . See [link] .

Questions & Answers

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
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
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
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply
Practice Key Terms 6

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Essential precalculus, part 1. OpenStax CNX. Aug 26, 2015 Download for free at http://legacy.cnx.org/content/col11871/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Essential precalculus, part 1' conversation and receive update notifications?

Ask