x/(x^2+x+1)=1/3=>1/(x+1+1/x)=1/3=>x+1/x=2=>(x+1/x)^2=4=>(x^2+1/x^2)=4-2=2所以(x^2)/(x^4+x^2+1)=1/(x^2+1/x^2+1)=1/(2+1)=1/3
解：由x/(x^2+x+1)=1/3可知x=1；代入所求式子：(x^2)/(x^4+x^2+1)=1/3
