x²-3x+1=0x²+1=3x同时除以xx+1/x=3(x+1/x)²=9x²+1/x²+2=9x²+1/x²=7x²/(x^4-x^2+1)分子分母同时除以x²=1/(x²-1+1/x²)=1/(7-1)=1/6