Show that:
or
![]()
Take;
and
It should be![]()
Now, the proof I've found is nasty
We have
Let's define
M divides any linear combination ( with integer coeficients) of those 2.
So M divides:i.e.
Again:Thus:
And this goes on:![]()
We keep on eliminating terms, the idea is to have only 1 term in the end.
Ifis even we eventually get:
( or the symmetric)
Whereas if n is odd:
But, since M divides a-b and (a,b)=1 thenand
thus we must have
![]()