x^2+3x-1=0
x^2-1=3x
x-1/x=3
(x-1/x)^2=9
x^2-2+1/x^2=9
x^2+1/x^2+2=13
(x+1/x)^2=13
x+1/x=±√13
x^2-1/x^2=(x+1/x)(x-1/x)=±√13x3=±3√13