x²-3x+1=0
同时除以x,得:
x-3+1/x=0
x+1/x=3
(x+1/x)²=9
x²+1/x²+2=9
x²+1/x²=7

x²/(x^4+x²+1)
=1/(x²+1+1/x²)
=1/(7+1)
=1/8