Use this to help you work it out.

First note that (Phi – 1/2)2 = Phi2 – Phi + 1/4
Using this we can write Phi2 – Phi – 1 as (Phi – 1/2)2 – 5/4
and since Phi2 – Phi – 1 = 0 then (Phi – 1/2)2 must equal 5/4
Taking square-roots gives (Phi – 1/2) = +(5/4) or –(5/4).
so Phi = 1/2 + (5/4) or 1/2 – (5/4).
We can simplify this by noting that (5/4) = 5/4 = 5/2

Posted By: tudders, Sep 6, 13:05:32