I wonder why the solution with Arithmetic progression is impossible.
a:=a+b
c:=c-d
...
...
and several times
isn't that equals to a:=a+bx
and c:=c-dx ??

Because they can stop after
a:=a+b
c:=c-d
...
...
a:=a+b

It equals to
a:=a+bx
c:=c-d(x-1)

Edited by author 13.03.2010 01:16