Register to reply

Write an exponential equation from this data (data table included)

Share this thread:
Jun13-10, 12:33 PM
P: 16
1. The problem statement, all variables and given/known data
- The following table gives the population of a city over time:

2. Relevant equations

I know this equation: y = a(b)x

and exponential growth: b = 1 + growth rate and b = 1 - decay rate

3. The attempt at a solution

I know from back in chapter 2 that first differences = linear model, second differences are the same = quadratic and if the 3rd differences are the same then its a cubic model...but that doesn't work here. I am completely do I find the model. Any hints/tips/methods will be greatly appreciated!! Thanks!!
Phys.Org News Partner Science news on
'Smart material' chin strap harvests energy from chewing
King Richard III died painfully on battlefield
Capturing ancient Maya sites from both a rat's and a 'bat's eye view'
Jun13-10, 03:58 PM
Sci Advisor
PF Gold
P: 39,682
There are two unknown constants in your formula, a and b. You need two equations to solve for two unknowns so pick two points (typically, it is best to endpoints, here 1954 and 1994).

That will give you [tex]132459= ab^{1954}[/tex] and [tex]514013= ab^{1994}[/tex]

It should be easy to see that dividing one equation by the other will eliminate a, leaving a single equation to solve for b.
Jun13-10, 11:58 PM
HW Helper
PF Gold
LCKurtz's Avatar
P: 7,717
Perhaps you are supposed to find a best least squares fit to the data?

Register to reply

Related Discussions
Simple Force problem(Picture and Graphical Data included.) Introductory Physics Homework 3
Steam table data vs experimental : Why the difference? General Engineering 8
C++ read/write data help Engineering, Comp Sci, & Technology Homework 1
Analysing Experimental Data (PHOTOS INCLUDED) Introductory Physics Homework 1
Write data on any surface ? Computing & Technology 13