PT \Leftrightarrow $\frac{(x+1).(x^2-x+1)-(x-1)(x^2+x+1)}{(x^2+x+1)(x^2-x+1)}=\frac{3}{x(x^4+x^2+1)}$
\Leftrightarrow $\frac{x^3+1-x^3+1}{(x^2+1)^2-x^2}=\frac{3}{x(x^4+x^2+1)}$
\Leftrightarrow $\frac{2}{x^4+x^2+1}=\frac{3}{x(x^4+x^2+1)}$
\Leftrightarrow $2x=3$
\Leftrightarrow $x=\frac{3}{2}$