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Hi,
I am trying to create a sheet to show the derivation of 2nd and 4th-order function derivatives as part of a 5-point finite difference scheme for a 1-D model (a continuous beam on an irregular foundation). I have isolated 2 simultaneous equations by using Taylor polynomials and would like to cast these in matrix form and then solve for each of the D-operators symbolically. Is there a simple way to do this or do I have to work with the ops manually?
thanks for any help,
Neil

Hi,
I'm trying to complete two questions. One question is using maple 'to solve the following systems of equations':
y=2x-5,y=2x^2+2x-21
I have entered the following code:
solve({y=2*x-5,y=2*x^2+2*x-21},{x,y});
The output I get is this:
{x = 2*RootOf(-2+_Z^2, label = _L14), y = 4*RootOf(-2+_Z^2, label = _L14)-5}
I have no idea what this means apart from the fact that it's wrong but i'm not sure where I have gone wrong.
The other question involves expanding the bracket (2x-3)^5
I've input:
expand(2*x-3)^5;
The output I get is:
(2*x-3)^5
Surely this is wrong???!

Hi Folks,
I have to believe this is an easy one, but it stumped me anyway. I'm trying to plot an ideal binary VLE curve for two components, and I have equations that describe both my x term and my y term as a function of temperature and pressure. Using the normal plot command, I can get x and y vs. T (if I specify pressure), but how do I get x vs. y (specifying pressure) and either plot T on a second Y axis or ignore it.
Thanks in advance. I have my simple worksheet available...
Fred

Vie
I had a few questions that I need help with:
1) I'm trying to write a procedure to solve a system of equations. To be specific, we are given 2 n x n matrices, say A and B by the user. We have two generic vectors in R^n, write them as x = [x1, x2, ..., xn] and y = [y1, y2, .., yn]. I want to solve for each of the yi's in terms of x'js for the equation A.x = B.y - how would I go about doing this?
2) So I get some answer to 1), say something like y = [x1-x3, x1+x2-x4, x1+x2, x3+x4] (n=4 for ease) . How could I easily take the coefficient matrix of the transpose of this vector? So, my final matrix would look like:

i need to solve a set of linear equations of size 7000x7000 using 128 digits, the system is sparsed. which of the "options" in LinearAlgebra[LinearSolve) is the the most efficient? is there more efficient builtin procedure for such computations?
thank's

Hi I have constructed a do loop to represent an epidemic described by 3 equations. I have plotted these using the initial conditions given.
If i want to identify the values of S[k], I[k] and R[k] at k=60 how do i enter this?
And how do i find out the exact point where the epidemic reaches its peak?

> p:=x->log[b](x);
p := x -> log[b](x)
> o:=x->b^x;
x
o := x -> b
> fsolve( p(x) = o(x) , {x,b} );
Error, (in fsolve) number of equations, 1, does not match number of variables, 2
I need to find the location (x,y) where they touch each other, thanks for the help.

In trying to answer the second question in

How to determine the order of an ODE? I have unsuccessfully tried to use

`select`

to filter out the appropiate parts of the differential equations.
In these attempts I have hit upon a behaviour of

`select`

I do not understand: In my opinion each of the following two code lines (or at the very least the second line) should return the differential expression itself:

select(has,diff(y(t),t),y);
select(has,diff(y(t),t),y(t));

But they do not; each line returns

`diff(y(t))`

, where the variable

`t`

with respect to which is being differentiated is missing. Why? Is it just me having fundamentally misunderstood something?

Although this question might seem silly to Maple experts, I cannot help asking, since despite a long search through Maple Help and Maple Guides I was not able to come across the answer. What I mean is this:
```
> eq1 := diff(y(t),t)-y(t)^2+y(t)*sin(t)-cos(t) = 0;
> # here I want some command that would return the order of eq1, i.e. 1
> something(eq1);
```

```
> eq2 := diff(y(t),`$`(t,2)) = y(t)*u(t) + diff(u(t),t);
> something(eq2,y); # this should return 2
> something(eq2,u); # this should return 1
```

Besides, I would also need the same for recurrent (shift) equations, i.e.

Hi,
I'm trying to solve a set of simultaneous equations, and the solutions I get are expressions of _Z. I'd be most grateful if anyone could explain what this means.

How would i go around solving these equations?
1.) **5(7y+3)=39**
2.) **20(21r+40)=100**

(I think this was posted in the wrong section of mapleprimes.)
Hi,
I have read the manual on saving to a file many times but it never works for me.
I am using Maple 10 on a Mac running MacOS 10.4.10.
I have copied the example from the manual and run that and it does work so I am quite confused.
Here is what I would like to do: I have a worksheet with lots of definitions,equations, lists, etc. and I would like to have these available on another worksheet. I have tried
> save nx; # nx is the name of my worksheet
then
> read nx;
Error, unable to read `nx`
I have the same problem with trying to save names e.g.

Hello.
I'm having a problem graphing the following parametric equations in 3d , together:
x=1-2*t
y=-t
z=3+t
and
x= 5+3*s-4*t
y=7-5*s-5*t
z=-2-s+6*t
Thanks, excuse-me my English, I’m foreigner

hello to everyone! I have a problem with the maple toolbox for matlab: i can't use the command setmaple to move my equations from matlab to maple. An example: i create two symbolic variables in matlab
>>syms x y;
then i set:
>>cos(x+y)
ans =
cos(x+y)
and now i try to move the equation to maple:
>>setmaple ('h',ans)
??? Undefined function or method 'setmaple' for input arguments of type 'sym'.
i'm using maple 11.01 and matlab 7.4.0. I tried updating toolbox for matlab but it didn't work. Some suggestions? Thanks...