x+1/x=3(x+1/x=3)^2=9x^2+1/x^2+2*x*1/x=9x^2+1/x^2=9-2=7x^2/x^4+1=1/(x^2+1/x^2)=1/7所以答案是1/7
x+1/x=3,(x+1/x)²=9，即x²+1/x²=7x^2/x^4+1分子分母同时除以x²得1/（x²+1/x²）=1/7
4/17
