> Is there any possibility to tell maxima to simplify above eq1 to this form > e(r+1, k+1) - e(r, k+1) = C . ( x(r, k+1) - x(r+1, k+1) ) I'm very sorry, the above should simplify to: e(r+1, k) - e(r, k) = C . ( x(r, k) - x(r+1, k) ) I do some modifications of my system equations and I do not change it when I send it.