November 21, 2019, 04:12:03 am

### AuthorTopic: Logs help  (Read 6631 times) Tweet Share

0 Members and 1 Guest are viewing this topic.

#### mandy

• Victorian
• Posts: 845
• Respect: +28
##### Logs help
« on: August 18, 2012, 11:01:02 pm »
0
Hi guys! I think I'm going crazy and can't do a single thing math-related anymore .. So I have to ask this for my sister:

Solve for x:

log5(x) = 16logx(5)

2009:
Biology [34]   Vietnamese [36]
2010:
English [48]   Chemistry [37]   Further [38]   Methods [39]   Specialist [29]
2010 ATAR: 97.20
2011: Bachelor of Biomedicine @ UniMelb

#### Jenny_2108

• Guest
##### Re: Logs help
« Reply #1 on: August 18, 2012, 11:52:05 pm »
+1
Hi guys! I think I'm going crazy and can't do a single thing math-related anymore .. So I have to ask this for my sister:

Solve for x:

log5(x) = 16logx(5)

loge(x)/loge(5)=16loge(5)/loge(x)
(loge(x))^2 = 16(loge(5))^2

(1) loge(x)=4loge(5)= loge(5)^4
x= e^(loge(5)^4)) = 5^4=625

(2) loge(x)=-4loge(5)
Solve as above, you get 1/625

Sorry I dont know how to type maths code. Hope you can interpret it or someone else may type again for me

« Last Edit: August 18, 2012, 11:55:12 pm by Jenny_2108 »

• Honorary Moderator
• ATAR Notes Legend
• Posts: 3175
• Respect: +323
##### Re: Logs help
« Reply #2 on: August 19, 2012, 12:08:51 am »
+12
loge(x)/loge(5)=16loge(5)/loge(x)
(loge(x))^2 = 16(loge(5))^2

(1) loge(x)=4loge(5)= loge(5)^4
x= e^(loge(5)^4)) = 5^4=625

(2) loge(x)=-4loge(5)
Solve as above, you get 1/625

Sorry I dont know how to type maths code. Hope you can interpret it or someone else may type again for me
I guess I'll go off topic and explain a bit of LaTeX, seeing that not enough people are using it / familiar with it (seriously cutting out the need to guess at ambiguity in statements like "log 2x + 1 / 2" makes answering questions that much easier). This post will be a bit long since I'll take it step by step

First step is that you can take each line and wrap it in [ tex ] tags. (you could also just use \align but have a look at that once you have the hang of $\LaTeX$ first)
Code: [Select]
$$loge(x)/loge(5)=16loge(5)/loge(x)$$$$(loge(x))^2 = 16(loge(5))^2$$(1) $$loge(x)=4loge(5)= loge(5)^4$$$$x= e^(loge(5)^4)) = 5^4=625$$(2) $$loge(x)=-4loge(5)$$Solve as above, you get $$1/625$$
Quote
$loge(x)/loge(5)=16loge(5)/loge(x)$

$(loge(x))^2 = 16(loge(5))^2$

(1) $loge(x)=4loge(5)= loge(5)^4$

$x= e^(loge(5)^4)) = 5^4=625$

(2) $loge(x)=-4loge(5)$

Solve as above, you get $1/625$

Let's fix up the subscripts and superscripts now. To do a superscript, you use the ^ symbol. To do subscript, you use _. If you want more than one character superscripted or subscripted, you stick it in curly braces: ^{20}

Code: [Select]
$$log_e(x)/log_e(5)=16log_e(5)/log_e(x)$$$$(log_e(x))^2 = 16(log_e(5))^2$$(1) $$log_e(x)=4log_e(5)= log_e(5)^4$$$$x= e^{log_e(5)^4} = 5^4=625$$(2) $$log_e(x)=-4log_e(5)$$Solve as above, you get $$1/625$$
Quote
$log_e(x)/log_e(5)=16log_e(5)/log_e(x)$

$(log_e(x))^2 = 16(log_e(5))^2$

(1) $log_e(x)=4log_e(5)= log_e(5)^4$

$x= e^{log_e(5)^4} = 5^4=625$

(2) $log_e(x)=-4log_e(5)$

Solve as above, you get $1/625$

Now let's fix up the fractions. To do a fraction, you can use \frac{numerator}{denominator}. You can also do something like 2 \over 12

Code: [Select]
$$\frac{log_e(x)}{log_e(5)}=\frac{16log_e(5)}{log_e(x)}$$$$(log_e(x))^2 = 16(log_e(5))^2$$(1) $$log_e(x)=4log_e(5)= log_e(5)^4$$$$x= e^{log_e(5)^4} = 5^4=625$$(2) $$log_e(x)=-4log_e(5)$$Solve as above, you get $${1} \over {625}$$
Quote
$\frac{log_e(x)}{log_e(5)}=\frac{16log_e(5)}{log_e(x)}$

$(log_e(x))^2 = 16(log_e(5))^2$

(1) $log_e(x)=4log_e(5)= log_e(5)^4$

$x= e^{log_e(5)^4} = 5^4=625$

(2) $log_e(x)=-4log_e(5)$

Solve as above, you get ${1} \over {625}$

That was fairly effortless and not that different to how you were already typing out maths. You can also do stuff like:
Code: [Select]
$$\int^{a}_{2b}(2x) \ dx$$ $$\pi$$$$Ca^{2+}_{(aq)} + 2e^- \leftrightharpoons Ca_{(s)}$$
$\int^{a}_{2b}(2x) \ dx$

$\pi$

$Ca^{2+}_{(aq)} + 2e^- \leftrightharpoons Ca_{(s)}$

List of LaTeX Resources
LaTeX typeset in Maths boards

#### Jenny_2108

• Guest
##### Re: Logs help
« Reply #3 on: August 19, 2012, 12:19:46 am »
+1
b^3 also sent me the maths code but I'm so lazy. It takes too much time. I type very slowly as well

So if I have to choose typing maths code or not answering, I think I'm gonna go with 2nd choice

Anyways, thanks a lot for your help, I'll learn when I have free time

#### TrueTears

• TT
• Honorary Moderator
• Great Wonder of ATAR Notes
• Posts: 16365
• Respect: +654
##### Re: Logs help
« Reply #4 on: August 19, 2012, 12:25:22 am »
0
b^3 also sent me the maths code but I'm so lazy. It takes too much time. I type very slowly as well

So if I have to choose typing maths code or not answering, I think I'm gonna go with 2nd choice

Anyways, thanks a lot for your help, I'll learn when I have free time
You should definitely take the time to learn LaTeX if you're considering to do anything related to science at uni. LaTeX is probably the most important skill I learnt on VN, to this day you don't know how many assignments and papers I've written using LaTeX lol
Currently studying: PhD in economics at MIT.

Interested in financial economics, econometrics, and asset pricing.

#### paulsterio

• ATAR Notes Legend
• Posts: 4829
• I <3 2SHAN
• Respect: +426
##### Re: Logs help
« Reply #5 on: August 19, 2012, 12:29:43 am »
+1
Haha, even though I know LaTeX, I find it so much faster to just use a WYSIWYG LaTeX editor - so just type in what you want using templates and it'll output that as a .tex file.

#### Jenny_2108

• Guest
##### Re: Logs help
« Reply #6 on: August 19, 2012, 12:30:25 am »
0
b^3 also sent me the maths code but I'm so lazy. It takes too much time. I type very slowly as well

So if I have to choose typing maths code or not answering, I think I'm gonna go with 2nd choice

Anyways, thanks a lot for your help, I'll learn when I have free time
You should definitely take the time to learn LaTeX if you're considering to do anything related to science at uni. LaTeX is probably the most important skill I learnt on VN, to this day you don't know how many assignments and papers I've written using LaTeX lol

Okayyyyyyyy I'll learn after finishing end-of-year exams!!!!!!! Not now anyways

#### Jenny_2108

• Guest
##### Re: Logs help
« Reply #7 on: August 19, 2012, 12:34:18 am »
0
Haha, even though I know LaTeX, I find it so much faster to just use a WYSIWYG LaTeX editor - so just type in what you want using templates and it'll output that as a .tex file.

I just spend like 3 mins to type the above answer but if I type LateX, it may take me 1 hr.

I'm not a patient person to sit here and struggle to type LateX even though I love maths and science

#### JinXi

• Victorian
• Posts: 818
• Respect: +90
• School: Camberwell High School
##### Re: Logs help
« Reply #8 on: August 19, 2012, 12:43:25 am »
0
I've learnt latex through this website. Really useful whenever you don't know the code to some symbol/layout.

Monash B.Aero Eng/Sci Discontinued in Sem2 2012 [2011-2015]

"I will always choose a lazy person to do a difficult job… because, he will find an easy way to do it." ~ Bill Gates
^ SNORLAX, I chooosee You!!!

• Honorary Moderator
• ATAR Notes Legend
• Posts: 3175
• Respect: +323
##### Re: Logs help
« Reply #9 on: August 19, 2012, 12:53:08 am »
+1
b^3 also sent me the maths code but I'm so lazy. It takes too much time. I type very slowly as well
Haha, I was hoping that I'd be able to show that it doesn't actually take too long for most things, for your post was just adding the LaTeX tags and then the code for the fractions really - which was writing \frac{16loge(5)}{loge(x)} instead of 16loge(5)/loge(x), or alternatively {16loge(5)} \over {loge(x)}. Yeah it looks a bit frightening at first, but it's pretty simple once you've used it 3 or 4 times.

For the superscripts and subscripts, you would have typed them out in the style required in the first place. You also get in the habit of typing things like log_e too. For stuff like integrals, matrices and more complex things, I can understand that it'd take a long time if you're not used it, that's fine.

For just regular algebra and fractions, though, I think it's easy enough to adapt to it.

Along the way you pick up on on little things like using \pi and \not{=} and \vec{a}, which you can look up a couple of times before you know how to do it, but that's not necessary for a lot of posts. It's really the fractions and not having to use excessive brackets in order to not be ambiguous where the advantage lies.

edit: By the way, my posts aren't really directed at you specifically, it's just something that's been on my mind for quite a while now.
« Last Edit: August 19, 2012, 12:58:14 am by laseredd »

#### Jenny_2108

• Guest
##### Re: Logs help
« Reply #10 on: August 19, 2012, 03:24:27 pm »
0
Yeah, if its only fraction or subscripts/superscripts, it can be typed easily but when all of them plus integral,etc,... are combined together,
I dont think I can type it quickly

#### charmanderp

• Honorary Moderator
• ATAR Notes Legend
• Posts: 3209
• Respect: +304
##### Re: Logs help
« Reply #11 on: August 19, 2012, 05:10:45 pm »
0
b^3 also sent me the maths code but I'm so lazy. It takes too much time. I type very slowly as well

So if I have to choose typing maths code or not answering, I think I'm gonna go with 2nd choice

Anyways, thanks a lot for your help, I'll learn when I have free time
You should definitely take the time to learn LaTeX if you're considering to do anything related to science at uni. LaTeX is probably the most important skill I learnt on VN, to this day you don't know how many assignments and papers I've written using LaTeX lol
University of Melbourne - Bachelor of Arts majoring in English, Economics and International Studies (2013 onwards)

#### Jenny_2108

• Guest
##### Re: Logs help
« Reply #12 on: August 21, 2012, 07:48:36 pm »
0
b^3 also sent me the maths code but I'm so lazy. It takes too much time. I type very slowly as well

So if I have to choose typing maths code or not answering, I think I'm gonna go with 2nd choice

Anyways, thanks a lot for your help, I'll learn when I have free time
You should definitely take the time to learn LaTeX if you're considering to do anything related to science at uni. LaTeX is probably the most important skill I learnt on VN, to this day you don't know how many assignments and papers I've written using LaTeX lol

I think its mainly in maths

#### charmanderp

• Honorary Moderator
• ATAR Notes Legend
• Posts: 3209
• Respect: +304
##### Re: Logs help
« Reply #13 on: August 21, 2012, 07:49:46 pm »
0
b^3 also sent me the maths code but I'm so lazy. It takes too much time. I type very slowly as well

So if I have to choose typing maths code or not answering, I think I'm gonna go with 2nd choice

Anyways, thanks a lot for your help, I'll learn when I have free time
You should definitely take the time to learn LaTeX if you're considering to do anything related to science at uni. LaTeX is probably the most important skill I learnt on VN, to this day you don't know how many assignments and papers I've written using LaTeX lol

I think its mainly in maths
Can be used for chemistry too though.
University of Melbourne - Bachelor of Arts majoring in English, Economics and International Studies (2013 onwards)

#### Jenny_2108

• Guest
##### Re: Logs help
« Reply #14 on: August 21, 2012, 07:54:01 pm »
0

I didnt say it wasnt used for Chem