\(x^6+3x^4+4x^2+1=\left(x^2+1\right)^3+x^2\ge\left(x^2+1\right)^3\)
\(x^6+3x^4+4x^2+1=\left(x^2+2\right)^3-\left(3x^4+8x^2+7\right)< \left(x^2+2\right)^3\)
\(\Rightarrow\left(x^2+1\right)^3\le x^6+3x^4+4x^2+1< \left(x^2+2\right)^3\)
\(\Rightarrow\left(x^2+1\right)^3=x^6+3x^4+4x^2+1\)
\(\Rightarrow x=0;y=0\)