# [LON-CAPA-dev] Installing Modules for LON-CAPA

Gerd Kortemeyer lon-capa-dev@mail.lon-capa.org
Mon, 26 Sep 2005 16:10:47 -0400

```Hi Donnell,

On Sep 26, 2005, at 3:33 PM, GARRETT, DONNELL MAZON wrote:

> Hi
>
> That was an example... maybe one that is too simple to show what I'm
> trying to do.
>
> Let's say we want to solve for x and y, and if we randomly generate A,
> B, C, D, E, and F, then
>
> xA + yB = C
> xD + yE = F
>
> how can we find x and y using an algorithm that we don't have to
> cut and
> paste into each and every problem.

Yep, you can use the .library mechanism (as Guy explained) to write
routines that you can then <import> into any problem.

But, what I was trying to suggest is building your problem the other
way around, i.e., randomly determine the solution first.

\$x=&random(-4,4,3);
\$y=&random(-4,7,3);

\$a=&random(4,8,1);
\$b=&random(4,8,1);
\$d=&random(5,9,1);

Now, when determining your \$e, you just need to make sure that the
second equation is not a multiple of the first:

\$e=\$d/\$a*\$b+&random(4,8,1);

Then calculate your \$c and \$f:

\$c=\$a*\$x+\$b*\$y;
\$f=\$d*\$x+\$e*\$y;

To your students, you just give \$a, \$b, \$c, \$d, \$e, and \$f, of
course. Solving an equation system is computing-intensive,
constructing one is not - and there is no reason why LON-CAPA needs
to do the same work that the students do.

But maybe the example is really too simple.

- Gerd.

```