题目:已知x+ 1/x =3,求x^2/(x^4+x^2+1).
请附上解题过程和思路
原式=1/8
x+ 1/x =3
(x^4+x^2+1)/x^2=x^2+1+1/x^2=(x+ 1/x )^2 -2+1=8
x^2/(x^4+x^2+1)=1/8