# simultaneous equations

• 04-14-2003
nic_elmo_13
simultaneous equations
how would i go about the following: read in three coefficents and the constant term for three simultaneous equations in three unknowns: aix+biy+ciz=di for i=1,2,3 find the solution (for x,y and z).any help would be very much appreciated!
• 04-14-2003
Magos
use linear algebra. Put the equations in matrix form (Ax = b) and then use gauss elimination. Make sure you get no zeros in the diagonal by using pivoting.

More in-depth info:
http://www.damtp.cam.ac.uk/user/fdl/...h98/linear.htm

If time is critical, you can first split A into two triangular matrices L & R (left triangular and right triangular):

LR = A
Ax = b

LRx = b
L(Rx) = b

Rx = y
Ly= b

First, solve Ly = b, then Rx = y. Since L and R are triangular, solving them will be easier.
• 04-14-2003
nic_elmo_13
matrices
ok thanks.i know how to do matrices by hand but how do i incorporate them into a program?i really do not understand programming!please help me!!
• 04-14-2003
Magos
Since you know the dimensions:
Code:

```typedef struct {   double _11, _12, _13;   double _21, _22, _23;   double _31, _32, _33; }Matrix3x3; typedef struct {   double _1;   double _2;   double _3; }Matrix1x3; Matrix3x3 A; Matrix1x3 b;```
Quote:

i really do not understand programming