We have these two sequences, defined as:
Xn+1= Xn + Yn and Yn+1=Xn-Yn
Find simple formulae for Xn and Yn. Don't even know how to start this... any help is welcome. I know it must be simple, but don't know how to do it. Usual difference equations I had were x smth and then I could use lambda exchange and find coefficients to solve it. This I don't know.