PT <=> \(\sqrt{\left(x-5\right)\left(x+5\right)}=2.\sqrt{x-5}\)
<=> \(\sqrt{x-5}.\sqrt{x+5}-2.\sqrt{x-5}=0\)
<=> \(\sqrt{x-5}\left(\sqrt{x+5}-2\right)=0\)
<=> \(\left[{}\begin{matrix}\sqrt{x-5}=0< =>x=5\\\sqrt{x+5}-2=0< =>x=-1\end{matrix}\right.\)
KL: \(x\in\left\{5;-1\right\}\)