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Author
Borsuc

Joined: 29 Dec 2005
Posts: 2466
Location: Bucharest, Romania
Borsuc
Anyone know such application available out there?

Let me explain:

I need some application to solve linear equation "formulas" for me -- i.e output is of the form (A+B)(C+D) or similar (not necessarily optimal, I can simplify it later myself). The main important idea is that it will operate on "symbols" rather than calculate digits.

All equations are solvable for all unknowns (i.e if we put it in a matrix, it has nxn rows and columns).

Why do I need this? I have some points (for the sake of an example, let's say 4 points), at specific locations (known), and I want to find out the coefficients for a function that walks through them.

Note: I might also need functions with multiple arguments (like bilinear function), so 4 points doesn't always mean a 3rd degree polynomial

Here the example equation (^ denotes power):

Code:
```Ax^3 + Bx^2 + Cx + D = p1
Ay^3 + By^2 + Cy + D = p2
Az^3 + Bz^2 + Cz + D = p3
Aw^3 + Bw^2 + Bw + D = p4    ```

Now I wish to find a formula to find out the A,B,C,D unknowns (coefficients). x,y,z,w and p1,p2,p3,p4 are known, and once I have the formula, I can replace them with their values (actually, they're variables ) and calculate the coefficients.

The question is, is such program available out there? (I might possibly need 4th or even higher degree polynomials, for more points, or multi-dimensional functions as well).

A bilinear function example:

Code:
```Ax + By + Cxy + D = p1
Au + Bv + Cuv + D = p2
Ao + Bp + Cop + D = p3
An + Bm + Anm + D = p4    ```
Again, the unknowns are A,B,C,D and the others are variables with some values stored, and I need some kind of formula for this.

A link to some program would be nice

If there is no such program available, then links to these 2 function examples (or even more functions) with written formulas is welcomed as well. Web page, .pdf, database, whatever

Yes I know I could solve them myself, but with substitution it's so hard and even Cramer's rule gets complicated on such equations, especially if we move on to higher degrees
25 Jul 2007, 18:54
MHajduk

Joined: 30 Mar 2006
Posts: 6034
Location: Poland
MHajduk
The_Grey_Beast wrote:
Anyone know such application available out there?
For example Maple or Mathematica.
25 Jul 2007, 19:11
Borsuc

Joined: 29 Dec 2005
Posts: 2466
Location: Bucharest, Romania
Borsuc
Thanks, I'll definetely take a look into them
25 Jul 2007, 19:55
Jack

Joined: 16 Feb 2005
Posts: 21
Jack
some free CAS Maxima , axiom and yacas
25 Jul 2007, 22:43
Borsuc

Joined: 29 Dec 2005
Posts: 2466
Location: Bucharest, Romania
Borsuc
Lots of thanks. Maxima seems very interesting, I'll try it tomorrow
26 Jul 2007, 19:53
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