PT $\Leftrightarrow x^4+2x^2+1=2x^2+2x+\frac{1}{2}$
$\Leftrightarrow (x^2+1)^2=\left ( \sqrt 2x+\frac{1}{\sqrt 2} \right )^2$
$\Leftrightarrow \left[ {\begin{matrix}
x^2+1= \sqrt 2x+\frac{1}{\sqrt 2} \\
x^2+1= -\sqrt 2x-\frac{1}{\sqrt 2} \end{matrix}} \right.$
$\Leftrightarrow \left[ {\begin{matrix} x^2-\sqrt 2x+1-\frac{1}{\sqrt 2} =0\\ x^2+1+\sqrt 2x+\frac{1}{\sqrt 2} =0 \quad \text{(vô nghiệm)} \end{matrix}} \right.$
$\Leftrightarrow x=\frac{1}{\sqrt 2 }\pm\sqrt{\frac{\sqrt 2 -1}{2}}$