$$L_n= \left (1 + \frac{\sqrt{5}}{2}\right)^n + \left (1 − \frac{\sqrt{5}}{2}\right)^n$$
How do you solve this? Where do you start?
$$L_n= \left (1 + \frac{\sqrt{5}}{2}\right)^n + \left (1 − \frac{\sqrt{5}}{2}\right)^n$$
How do you solve this? Where do you start?
Copyright © 2021 JogjaFile Inc.
Lets do it by induction. Clearly, $((1+\sqrt{5})/2)+((1-\sqrt{5})/2) =1=L_1$. Suppose this is true upto $n=k$. Consider,
$L_{n+1}=L_n+L_{n-1}=((1+\sqrt{5})/2)^n+((1-\sqrt{5})/2)^n + ((1+\sqrt{5})/2)^{n-1}+((1-\sqrt{5})/2)^{n-1} = ((1+\sqrt{5})/2)^{n-1}(((1+\sqrt{5})/2)+1) + ((1-\sqrt{5})/2)^{n-1}(((1-\sqrt{5})/2)+1) = ((1+\sqrt{5})/2)^{n-1}((1+\sqrt{5})/2)^2 + ((1-\sqrt{5})/2)^{n-1}((1-\sqrt{5})/2)^2 = ((1+\sqrt{5})/2)^{n+1} + ((1-\sqrt{5})/2)^{n+1} $.