If you are setting problems to challenge people put them in one of the Lounge groups.
These groups are for people who want help with stuff they don't know the answer to.
How about any combination of a = 0, c = -b where b is any real number.
-Dan
I'm afraid it won't work...
Despite the fact, that in equation I wrote (a-2)(a-1).... you can pick eg. a=1 b=2 c=-1 and it seems to be correct,when you put that numbers to original equations it's incorrect...