Before we begin the proof of Binet’s formula, it is prudent first to consider where it came from.
The term (1±
√
5)
2
is easily recognized as the solutions to the quadratic equation x
2 = x + 1. If
we wish we may rewrite Binet’s formula in terms of the real values φ =
(1+√
5)
2
and φ0 =
1−
√
5
2
as follows: