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Maths help needed!

EDIT: I figured out my first problem, now I just need to figure out this one.

[url=http://i.imgur.com/fIfFl.png]Maths problem [/url]
The answer is supposedly 'A'. But how do you get that?

By the way, this topic is Cubics and quartics.

Thanks in advance.

May 26, 2011

3 Comments • Newest first

deadlyzombie

[quote=InsainBowman]*starts doing work*
25=25*e^(0*r) // time is 0 , r is rate of change
0=25*e^(900*r) // when time is 900
f(x)=25*e^(t*r)

this is trusting that you are using e.
and with
0=25*e^(900*r)
you should easily be able to fight what constant r is.[/quote]

What? Is that physics or something? I don't know what e or r are...
This is Unit 1 Methods (Australia)

Reply May 26, 2011
InsainBowman

*starts doing work*
25=25*e^(0*r) // time is 0 , r is rate of change
0=25*e^(900*r) // when time is 900
f(x)=25*e^(t*r)

this is trusting that you are using e.
and with
0=25*e^(900*r)
you should easily be able to fight what constant r is. to me it seems like r is -0.3 to me

Reply May 26, 2011 - edited
Josiah

*reserves spot*

Reply May 26, 2011 - edited