For the Fibonacci sequence Fn=Fn−1+Fn−2F_n = F_{n-1} + F_{n-2}Fn=Fn−1+Fn−2, which value is the golden ratio ϕ\phiϕ?
1+52\frac{1+\sqrt{5}}{2}21+5
1−52\frac{1-\sqrt{5}}{2}21−5
5\sqrt{5}5
1.51.51.5