Hi,

Thanks for quick answer.

Ok, i and j are indexes, so I can say the same as you. Yes, they can be equal.

This is actually differential equation which calculate change of temperature between room temperature and outside temperature.

Parameters are B(capacity of the room) and U(conductivity).

ics are Ti, Tj and Hi. I attach here how I write this in Maple and please let me know do I need to add something.

> eq := B*(diff(T[i](t), t)) = U*(T[i](t)-T[j](t))+H[i](t);
         / d         \                                  
       B |--- T[i](t)| = U (T[i](t) - T[j](t)) + H[i](t)
         \ dt        /                                  

isolate(B*(diff(T[i](t), t)) = U*(T[i](t)-T[j](t))+H[i](t), diff(T[i](t), t));
          d            U (T[i](t) - T[j](t)) + H[i](t)
         --- T[i](t) = -------------------------------
          dt                          B