Verified answer

(2-sqrt(3))^x=t

t^2-4t+1<=0

[2-sqrt(3);2+sqrt(3)]

(2-sqrt(3))^x>=2-sqrt(3)

x<=1

(2-sqrt(3))^x<=2+sqrt(3)

(2-sqrt(3))^x<=(2-sqrt(3))^-1

x>=-1

[-1;1]