2 problems im working on

You can show that it exists by construction (and that by induction on n). Is that enough to go on?

Intro to Math Proofs class? :)

Probably unnecessary to add this (familiar fact to you) now, but every proof by induction involves:

1. writing down an induction hypothesis
2. proving it for the smallest n
   and 
3. proving the (n+1)th results follows from the n'th

That's easy X2

Yes, it's easy, but I had forgotten Taylor's Theorem.

Quite right Elroch. I see now how to do it by induction.

The uniqueness, although by no means hard, isn't completely trivial.

Regards to all :)

Oh yeah with the taylor theorom you have to look at the coefficient value of x2. X2 = 5a '

You know what I mean.