ATAR Notes: Forum

VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: mangmang712 on April 08, 2009, 02:06:59 pm

Title: more questions!
Post by: mangmang712 on April 08, 2009, 02:06:59 pm: Is stuck on this question:

$3x=10^-0.3x$

thanks in advance .. will probably be posting more soon :uglystupid2:
Title: Re: more questions!
Post by: TrueTears on April 08, 2009, 02:09:57 pm: $3x = 10^{\frac{-3x}{10}}$

You have to use calculator to solve that, and it will only yield an approximated answer (decimal)

EDIT: better to use nSolve(...) if you are using TI-89
Title: Re: more questions!
Post by: mangmang712 on April 08, 2009, 02:13:19 pm: no its meant to be: 10 to the power of -0.3x

sorry
Title: Re: more questions!
Post by: mangmang712 on April 08, 2009, 02:19:00 pm: is this right so far:

$loge3x = -0.3xloge10$
$-0.3x = loge3x/loge10$

.. if i was to solve algebraically before referring to the calc
Title: Re: more questions!
Post by: TrueTears on April 08, 2009, 02:27:27 pm: I meant you can't solve it algebraically this question no matter what, ie You can't get an exact answer, there isn't one. You have to use calculator.
Title: Re: more questions!
Post by: mangmang712 on April 08, 2009, 02:31:24 pm: and also this question; if $f(4)=6$ and $f'(4) =2,$ find $g'(4)$ if:
$g(x)=f(x)/x$
Title: Re: more questions!
Post by: mangmang712 on April 08, 2009, 02:33:53 pm: thanks truetears .. sorry about the confusion. i was also struggling with latex :-[
Title: Re: more questions!
Post by: TrueTears on April 08, 2009, 02:34:40 pm: Quote from: mangmang712 on April 08, 2009, 02:33:53 pm
thanks truetears .. sorry about the confusion. i was also struggling with latex :-[

No problems XD
Title: Re: more questions!
Post by: NE2000 on April 08, 2009, 02:44:21 pm: Quote from: mangmang712 on April 08, 2009, 02:31:24 pm
and also this question; if $f(4)=6$ and $f'(4) =2,$ find $g'(4)$ if:
$g(x)=f(x)/x$

What's the question want you to find??

EDIT: sorry, didn't read properly
Title: Re: more questions!
Post by: mangmang712 on April 08, 2009, 02:47:27 pm: im not sure what u mean... i need to find $g'(4)$ if $g(x) = f(x)/x$ using the information provided
Title: Re: more questions!
Post by: mangmang712 on April 08, 2009, 02:48:53 pm: thats all the info that is given. its in the 'essentials' textbook, chpt 9K, Q5(b) if that helps
Title: Re: more questions!
Post by: TrueTears on April 08, 2009, 02:57:11 pm: $g'(x) = \frac{xf'(x)-f(x)}{x^2}$ (Using the quotient rule)

$g'(x) = \frac{4 \times 2 -6}{16} = \frac{1}{8}$
Title: Re: more questions!
Post by: mangmang712 on April 08, 2009, 03:00:00 pm: Thanks heaps!! :)
Title: Re: more questions!
Post by: NE2000 on April 09, 2009, 10:35:42 am: Quote from: mangmang712 on April 08, 2009, 02:47:27 pm
im not sure what u mean... i need to find $g'(4)$ if $g(x) = f(x)/x$ using the information provided

sorry, didn't read the question properly
Title: Re: more questions!
Post by: mangmang712 on April 09, 2009, 04:21:48 pm: Quote from: NE2000 on April 09, 2009, 10:35:42 am
Quote from: mangmang712 on April 08, 2009, 02:47:27 pm
im not sure what u mean... i need to find $g'(4)$ if $g(x) = f(x)/x$ using the information provided

sorry, didn't read the question properly

thats ok :) ... its a confusing question!