Proof of: if sqrt(5n^2+4) or sqrt(5n^2-4) is an integer, then n is Fibonacci?

[nomadreid]

I saw the conjecture
if sqrt(5n^2+4) or sqrt(5n^2-4) is an integer, then n is Fibonacci
(a) has this conjecture been proven?
(b) has it been disproven?
(c) if (a), what is the proof, or a link to the proof, or at least a kick-start to the proof?
Thanks.

 

[galactus]

Here is a link with some Fibonacci-related proofs:

http://www.fq.math.ca/Scanned/10-4/advanced10-4.pdf

look at page 5

 

[nomadreid]

Fibonacci Proof: thanks

Thanks, galactus, that's perfect.