Hi all.

When I need to prove with induction that an equality exist, for example:
http://i42.photobucket.com/albums/e316/K007/math/simpleN.gif

I don't have no problem as I only got one variable (n in this case).

But when I got for example :
prove that all Natural numbers can be presented as :
http://i42.photobucket.com/albums/e316/K007/math/2i.gif
when A is an infinite group of Natural numbers.

I don't understand how to make from it an equality I can work with induction as I got more then one variable.

* I don't want help of solving the problem, I only want help of understanding how to approach this kind of problems, if someone got a simple example that can help me understand how to approach such type of problems it will be even better.

thanks in advanced.

It is a little trickier than the standard example you showed, but look here:

http://faculty.salisbury.edu/~kmshannon/math300/distinctpowers.pdf

galactus thanks, I see it is really tricky.