x^2-√5x+1=0
x^2+1=√5 x
等式两边同时除以x
x+1/x=√5
(x+1/x)^2=(√5)^2
x^2+1/x^2+2=5
x^2+1/x^2=3
x^2+1/x^2-2=1
(x-1/x)^2=1
x-1/x=±1