Rules for combining DEs

Does anyone one know the rules for combing Differential Equations?

Combining

(2)
\frac{dj}{dx} = -C'\frac{dV}{dt} ;

and

(3)
\frac{dV}{dx}=-L'\frac{dj}{dt} ;

I need to get:

L'C'\frac{d^{2}V}{dt^{2}} = \frac{d^{2}V}{dx^{2}} ;

L' and C' are conductance and capacitance per unit length, and d is intended to represent lower case delta.

The problem concerns transmission lines.
FatherX, Exorcist
  • loscha

Packin Heat!

What calculators do you own and use?

I have (and use)
Texas Instruments:
TI-84+, TI-89 Titanium, TI-30X IIB (a normal scientific, I have the white/silvery one, but, would love to get a purple/green/blue one, too) and a TI-80 which I got for $5 at a hock shop because it was cute and twee and baby sized.
Casio:
FX-100d quite a rare one. I have 2. It has hex, milli micro nano pico kilo mega symbols on some buttons (very bloody useful for electronics engineering)

Slide Rules:
Three, various kinds. Favourite is a Hemmi (Earnest) my then best friend got me from an op shop she worked at (with it's manual).

Computer:
A really old version of Derive (dos), copied from the computers at my high school back in 1991.
I'm starting to get into YACAS, which I am finding useful.
I've used dodgies of Matlab and Mathematica, but, I'm not good enough at Math to really get maximum value from them.
FatherX, Exorcist
  • loscha

Two Banners





OK, they're not much, but, I thought I'd make some ditzy banners for people to put on their userinfo if they felt compelled to do so. They are made with TI calculator fonts.
FatherX, Exorcist
  • loscha

(no subject)

Poll #907774 How Do You?

What tool do you primarily use to do your math stuff?

Scientific Calculator
3(16.7%)
Graphing Calculator
4(22.2%)
Spreadsheet (Excel, Open Office, 123)
1(5.6%)
Open Source Math Package (YACAS, etc)
1(5.6%)
Matlab, Mathematica, Maple, Derive
1(5.6%)
Pen and Paper
7(38.9%)
Programming Language (please specify)
1(5.6%)
Other (please list below)
0(0.0%)
Specifically This (please list below)
0(0.0%)

Expansion of Q1

I Do Math

Because of My Course (Tertiary, Tafe, University)
6(35.3%)
Because I like It
6(35.3%)
For My Job
2(11.8%)
I need to (for values of need approaching psychological compulsion)
2(11.8%)
I'm a Secondary School Student
1(5.9%)
Other (please specify below)
0(0.0%)

Expansion of Q3

I have the following qualifications

Tertiary Degree (math related)
1(10.0%)
Incompleted Tertiary
2(20.0%)
Completed Secondary School
5(50.0%)
It's my hobby, I just tinker
2(20.0%)
I'm a computer programmer
0(0.0%)

Helping others

I'm here to help others
1(11.1%)
I'm here to get help
1(11.1%)
A bit of both
4(44.4%)
Here to see how this thing pans out
2(22.2%)
I'm here cause I want to stalk other memers of this group
1(11.1%)
FatherX, Exorcist
  • loscha

(no subject)

Hi all, my name is loscha.
I like mathematics.
I'm not extremely good at it, I don't have a degree, but, I enjoy it.
I enjoy helping other people with what I can.

This is a community for people to help others with (probably simple) math problems.

Not everyone knows how to use a normal calculator to work out what 17.25% discount on $35.50 is.

Hopefully, We can help.

I personally am a Wikipedian, and a Texas Instruments graphing calculator user, and somewhat of a collector of old calculators.
I bet I could add up the change in your purse very fast.