x²-3x+1=0同除x,得：x-3+1/x=0则：x+1/x=3(x+1/x)²=x²+1/x²+2=9所以：x²+1/x²=7x²/(x^4+x²+1),分子分母同除x²,得：x²/(x^4+x²+1)=1/(x²+1+1/x²),...