operations on polynomial expressions

> Example:
> x(y+z)+c xy -> (c+1)xy + xz
> (c does not have to be a number)

You can do this by

(%i3) x*(y+z)+c*x*y;
(%o3) x*(z+y)+c*x*y
(%i4) format(%, %poly(x,y,z));
(%o4) x*z+(c+1)*x*y

In case you want to learn more about format package I sent a link to
the manual in another post.

Andrej