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November 08, 2025, 01:51:12 pm
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Author Topic: Logarithm Help  (Read 3547 times)  Share 

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dejan91

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Logarithm Help
« on: February 20, 2009, 05:02:52 pm »
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4ex + 9e-x = 12

Thanks :)
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kamil9876

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Re: Logarithm Help
« Reply #1 on: February 20, 2009, 05:27:07 pm »
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multiply every term by e^x. Then you will get some term with e^2x and one with e^x, plus another thats just a constant. let e^x=a and notice that a quadratic forms which you should be able to solve. Once a is solved, logarithms will allow u to find x
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dejan91

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Re: Logarithm Help
« Reply #2 on: February 20, 2009, 05:31:49 pm »
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Awesome thanks.
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dejan91

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Re: Logarithm Help
« Reply #3 on: March 07, 2009, 11:24:04 am »
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Solve for and , where , and .

Help please.
« Last Edit: March 07, 2009, 12:52:12 pm by dejan91 »
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hard

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Re: Logarithm Help
« Reply #4 on: March 07, 2009, 12:49:20 pm »
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where did the t come from. do you mean when x =0 and x =10?
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dejan91

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Re: Logarithm Help
« Reply #5 on: March 07, 2009, 12:53:06 pm »
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Oh shit, sorry. The book has T and t, since they represent Temperature and time, but i put in x for t in one part.
Edited it.
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Damo17

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Re: Logarithm Help
« Reply #6 on: March 07, 2009, 07:00:16 pm »
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Quote from: dejan91 on March 07, 2009, 11:24:04 am

Solve for and , where , and .

Help please.

Firstly when .
If this is question 11 from Heinemann exercise 2.5:
A patient suffering with hypothermia after being lost in the snow for 2 days is covered in thermal blankets and warmed so that his body temperature can return to normal levels. The change in body temperature from the initial temperature that occurs during thermal treatment is modelled by the equation where t represents the time in minutes. The initial body temp is and it reaches ten minutes after treatment is initiated.

                 ......1

              ......2

First work out b:




Work out A now:


 

They are the right answers for this question from heinemann.
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dejan91

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Re: Logarithm Help
« Reply #7 on: March 08, 2009, 11:15:55 am »
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Yup that was the Heinemann question I just cbf'd writing the whole thing out. Thanks for that by the way.
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dejan91

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Re: Logarithm Help
« Reply #8 on: April 21, 2009, 09:14:34 pm »
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Help?

Given that where , find the value of such that .
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Mao

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Re: Logarithm Help
« Reply #9 on: April 21, 2009, 09:24:27 pm »
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...? x is not specified?
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TrueTears

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Re: Logarithm Help
« Reply #10 on: April 21, 2009, 09:24:36 pm »
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(treating sin(a) as a constant because we are differentiating with respect to x)







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dejan91

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Re: Logarithm Help
« Reply #11 on: April 21, 2009, 10:14:38 pm »
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Ah damn sorry Mao, meant to be not . But now I see, so when you substitue x = 0, a = 0.524 (which is what the book had).

The part that confused me was that I didn't know to keep as a constant. I get it now thanks TT :)
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dejan91

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Re: Logarithm Help
« Reply #12 on: June 25, 2009, 12:48:45 am »
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Simplify: . I get to a point where I'm just not sure what to do, or even if it's right.
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Re: Logarithm Help
« Reply #13 on: June 25, 2009, 08:23:12 am »
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im not sure if u can simplify it further
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TrueTears

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Re: Logarithm Help
« Reply #14 on: June 25, 2009, 04:44:01 pm »
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Quote from: Flaming_Arrow on June 25, 2009, 08:23:12 am










im not sure if u can simplify it further
Further simplify:



Hence



But I'm sure FA's final answer is perfectly acceptable.

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