((√5-2)(√5+2))^(x+1)>=2((√5+2)^(x+1))²-(√5+2)^(x+1)

(√5+2)^(x+1)=y

1>=2y^2-y

2y^2-y-1<=0

[-1/2;1]

-1/2<=(√5+2)^(x+1)<=1

x (-∞;-1]