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non-linear assessment..need help (1 Viewer)

nanoose

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I have an assessment on non-linear functions where i have to make-up an equation and draw a graph for a group of data...I dun no what to do...can sum1 plz help me
 

Trev

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im not totally sure about the group of data part
but can't you just make up an equation that is non-linear, ie. y=x^3 - x^2 + x - 1
and graph it? maybe the group of data means a table of values? eh???
 

nanoose

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ok so i use da data as a table of values but how do i make up the equation and chose 2 suitable non-linear models to graph it on...i dun no wat to do i am soooo stressed...
 

Trev

stix
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i dont have a clue what your going on about;
from what i gather, making up an equation, making a table of values, and graphing it on paper, is not a difficult task!
 

PC

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What do you mean by non-linear models? Do you have to think of some sort of example?

For an upside down parabola, you can think of the area of a rectangle, where its perimeter is fixed. For example, the perimeter might be 60 sq cm, so A = x(30 - x) = 30x - x^2.

For an exponential equation y = a^x, you can graph the balance each year in a compound interest account. For example, let P=100 and r=0.10, so A = P(1 + r)^n = 100(1+0.10)^n = 100*(1.1)^n.
 

nanoose

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ok were given a task about some island that is running out of water and we know when the island was first populated and some data on the island population's increase over the last 3 centuries...like u said i should use it as a table of values...im just having difficulty coming up or making up the equation...i got sum tutor help from the institue of math and they said just to plot the points and draw curve and interpret and substitute. But i still dont get how to make up an equation for quadratics, cubics etc....is substitution all that i need to do, from the graph? thanx ssssssooooooooooo much......
 

PC

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Gee ... I wonder what island they're talking about!

Sounds complicated. Sounds like an exponential equation, but two of them, one for the population increase and another for the water supply.

Can you attach the exact question?
 

nanoose

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The island of minniwater was first populated in the year 1775.
2.5 000 people emigrated to minniwater on 1/6/1775 to find an abbundant supply of water and a naturally formed dam in the mountain range on the island
a linear equation was developed that related the water remaining in the dam(assuming no rain) as being: W=60-8.5t
where t is in centuries and W is the amount of water remaining in the dam (model assumes each person used 1ML of water per year)
The first census of the island took place 42 years after they arrived
All subsequent censuses were recorded as time since arrival

here is the population data:

Year (centuries) since colonisation
0.42
0.83
1.1
1.25
1.6
1.77
2.15

Population (thousands)
4.03
605
8.2
10.5
16.9
21.4
29

and these are da q's we have to do:

1.graph the population data, ensure sufficent axis for plotting upto 3 centuries
2.Develop 2 non-linear models for the relationship between time and poulation- coefficents should be determined to 3 sig figs
3. Using your model prdict the populations 240yrs after population
4. Explain for what period of time your model is valid
5. Complete a table of values for t between 0 and 3 centuries and plot this on the same axes as the population data (W=60-8.5t)
6. Will the countyr run out of water?if so what year?
it takes 5 years to build a desalination plant should they construct a plant and if so when?

THANXS SOO MUCH email me or wateva cause i can use any help.....
 

Trev

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lol, ive got no clue what this is about! :p
damn general, questions are so confusing!
haha kinda off topic, but i saw this physics question today along the lines of "helga took steroids, her gonads have now shrunk making her muscles bigger, how far could she throw.......etc"
lol, like wtf?
 

nanoose

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no need to tell me how stupid sum things are ive got some living proof of it..and its due next tuesday...
 

PC

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Have a look at the attachment.

This is a pretty poor question - great idea - but probably needs to be simplified a little. There's no chance you'll EVER need to worry about something so complex in this course. Maybe next year at Uni...

Hope this helps.

I usually enjoy working through questions for people ... but not this one!
 

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