$\left\{\begin{matrix}P=\frac{\sqrt{56x^{3}-56x^{2}+1}+1}{28x}\text{; }P=\frac{-\sqrt{56x^{3}-56x^{2}+1}+1}{28x}\text{, }&x\neq 0\\P=0\text{, }&x=0\end{matrix}\right.$

$x=-\frac{\sqrt{196P^{4}+28P^{2}-4P+1}}{2}+7P^{2}+\frac{1}{2}$
$x=\frac{\sqrt{196P^{4}+28P^{2}-4P+1}}{2}+7P^{2}+\frac{1}{2}$

$\left\{\begin{matrix}P=\frac{\sqrt{56x^{3}-56x^{2}+1}+1}{28x}\text{; }P=\frac{-\sqrt{56x^{3}-56x^{2}+1}+1}{28x}\text{, }&x\neq 0\text{ and }56x^{3}-56x^{2}+1\geq 0\\P=0\text{, }&x=0\end{matrix}\right.$

$x=-\frac{\sqrt{196P^{4}+28P^{2}-4P+1}}{2}+7P^{2}+\frac{1}{2}$
$x=\frac{\sqrt{196P^{4}+28P^{2}-4P+1}}{2}+7P^{2}+\frac{1}{2}\text{, }196P^{4}+28P^{2}-4P+1\geq 0$