x/(x^2-x-1)=1/8
x^2-x-1=8x
x^2-1=9x(平方)
(x^2-1)^2=81x^2
x^4-2x^2+1=81x^2
x^4-x^2+1=82x^2
x^2/(x^4-x^2+1)=1/82